OK, let's work through this together. We're starting with 990 and we're going to multiply it by 141, which means we add 990 to itself 141 times.
Step 1: 0 + 990 = 990
Step 2: 990 + 990 = 1980
Step 3: 1980 + 990 = 2970
Step 4: 2970 + 990 = 3960
Step 5: 3960 + 990 = 4950
Step 6: 4950 + 990 = 5940
Step 7: 5940 + 990 = 6930
Step 8: 6930 + 990 = 7920
Step 9: 7920 + 990 = 8910
Step 10: 8910 + 990 = 9900
Step 11: 9900 + 990 = 10890
Step 12: 10890 + 990 = 11880
Step 13: 11880 + 990 = 12870
Step 14: 12870 + 990 = 13860
Step 15: 13860 + 990 = 14850
Step 16: 14850 + 990 = 15840
Step 17: 15840 + 990 = 16830
Step 18: 16830 + 990 = 17820
Step 19: 17820 + 990 = 18810
Step 20: 18810 + 990 = 19800
Step 21: 19800 + 990 = 20790
Step 22: 20790 + 990 = 21780
Step 23: 21780 + 990 = 22770
Step 24: 22770 + 990 = 23760
Step 25: 23760 + 990 = 24750
Step 26: 24750 + 990 = 25740
Step 27: 25740 + 990 = 26730
Step 28: 26730 + 990 = 27720
Step 29: 27720 + 990 = 28710
Step 30: 28710 + 990 = 29700
Step 31: 29700 + 990 = 30690
Step 32: 30690 + 990 = 31680
Step 33: 31680 + 990 = 32670
Step 34: 32670 + 990 = 33660
Step 35: 33660 + 990 = 34650
Step 36: 34650 + 990 = 35640
Step 37: 35640 + 990 = 36630
Step 38: 36630 + 990 = 37620
Step 39: 37620 + 990 = 38610
Step 40: 38610 + 990 = 39600
Step 41: 39600 + 990 = 40590
Step 42: 40590 + 990 = 41580
Step 43: 41580 + 990 = 42570
Step 44: 42570 + 990 = 43560
Step 45: 43560 + 990 = 44550
Step 46: 44550 + 990 = 45540
Step 47: 45540 + 990 = 46530
Step 48: 46530 + 990 = 47520
Step 49: 47520 + 990 = 48510
Step 50: 48510 + 990 = 49500
Step 51: 49500 + 990 = 50490
Step 52: 50490 + 990 = 51480
Step 53: 51480 + 990 = 52470
Step 54: 52470 + 990 = 53460
Step 55: 53460 + 990 = 54450
Step 56: 54450 + 990 = 55440
Step 57: 55440 + 990 = 56430
Step 58: 56430 + 990 = 57420
Step 59: 57420 + 990 = 58410
Step 60: 58410 + 990 = 59400
Step 61: 59400 + 990 = 60390
Step 62: 60390 + 990 = 61380
Step 63: 61380 + 990 = 62370
Step 64: 62370 + 990 = 63360
Step 65: 63360 + 990 = 64350
Step 66: 64350 + 990 = 65340
Step 67: 65340 + 990 = 66330
Step 68: 66330 + 990 = 67320
Step 69: 67320 + 990 = 68310
Step 70: 68310 + 990 = 69300
Step 71: 69300 + 990 = 70290
Step 72: 70290 + 990 = 71280
Step 73: 71280 + 990 = 72270
Step 74: 72270 + 990 = 73260
Step 75: 73260 + 990 = 74250
Step 76: 74250 + 990 = 75240
Step 77: 75240 + 990 = 76230
Step 78: 76230 + 990 = 77220
Step 79: 77220 + 990 = 78210
Step 80: 78210 + 990 = 79200
Step 81: 79200 + 990 = 80190
Step 82: 80190 + 990 = 81180
Step 83: 81180 + 990 = 82170
Step 84: 82170 + 990 = 83160
Step 85: 83160 + 990 = 84150
Step 86: 84150 + 990 = 85140
Step 87: 85140 + 990 = 86130
Step 88: 86130 + 990 = 87120
Step 89: 87120 + 990 = 88110
Step 90: 88110 + 990 = 89100
Step 91: 89100 + 990 = 90090
Step 92: 90090 + 990 = 91080
Step 93: 91080 + 990 = 92070
Step 94: 92070 + 990 = 93060
Step 95: 93060 + 990 = 94050
Step 96: 94050 + 990 = 95040
Step 97: 95040 + 990 = 96030
Step 98: 96030 + 990 = 97020
Step 99: 97020 + 990 = 98010
Step 100: 98010 + 990 = 99000
Step 101: 99000 + 990 = 99990
Step 102: 99990 + 990 = 100980
Step 103: 100980 + 990 = 101970
Step 104: 101970 + 990 = 102960
Step 105: 102960 + 990 = 103950
Step 106: 103950 + 990 = 104940
Step 107: 104940 + 990 = 105930
Step 108: 105930 + 990 = 106920
Step 109: 106920 + 990 = 107910
Step 110: 107910 + 990 = 108900
Step 111: 108900 + 990 = 109890
Step 112: 109890 + 990 = 110880
Step 113: 110880 + 990 = 111870
Step 114: 111870 + 990 = 112860
Step 115: 112860 + 990 = 113850
Step 116: 113850 + 990 = 114840
Step 117: 114840 + 990 = 115830
Step 118: 115830 + 990 = 116820
Step 119: 116820 + 990 = 117810
Step 120: 117810 + 990 = 118800
Step 121: 118800 + 990 = 119790
Step 122: 119790 + 990 = 120780
Step 123: 120780 + 990 = 121770
Step 124: 121770 + 990 = 122760
Step 125: 122760 + 990 = 123750
Step 126: 123750 + 990 = 124740
Step 127: 124740 + 990 = 125730
Step 128: 125730 + 990 = 126720
Step 129: 126720 + 990 = 127710
Step 130: 127710 + 990 = 128700
Step 131: 128700 + 990 = 129690
Step 132: 129690 + 990 = 130680
Step 133: 130680 + 990 = 131670
Step 134: 131670 + 990 = 132660
Step 135: 132660 + 990 = 133650
Step 136: 133650 + 990 = 134640
Step 137: 134640 + 990 = 135630
Step 138: 135630 + 990 = 136620
Step 139: 136620 + 990 = 137610
Step 140: 137610 + 990 = 138600
Step 141: 138600 + 990 = 139590

So, 990*141 = 139590