OK, let's crack this. We're given 90 and our task is to multiply it by 68. Essentially, we'll be adding 90 to itself 68 times.
Step 1: 0 + 90 = 90
Step 2: 90 + 90 = 180
Step 3: 180 + 90 = 270
Step 4: 270 + 90 = 360
Step 5: 360 + 90 = 450
Step 6: 450 + 90 = 540
Step 7: 540 + 90 = 630
Step 8: 630 + 90 = 720
Step 9: 720 + 90 = 810
Step 10: 810 + 90 = 900
Step 11: 900 + 90 = 990
Step 12: 990 + 90 = 1080
Step 13: 1080 + 90 = 1170
Step 14: 1170 + 90 = 1260
Step 15: 1260 + 90 = 1350
Step 16: 1350 + 90 = 1440
Step 17: 1440 + 90 = 1530
Step 18: 1530 + 90 = 1620
Step 19: 1620 + 90 = 1710
Step 20: 1710 + 90 = 1800
Step 21: 1800 + 90 = 1890
Step 22: 1890 + 90 = 1980
Step 23: 1980 + 90 = 2070
Step 24: 2070 + 90 = 2160
Step 25: 2160 + 90 = 2250
Step 26: 2250 + 90 = 2340
Step 27: 2340 + 90 = 2430
Step 28: 2430 + 90 = 2520
Step 29: 2520 + 90 = 2610
Step 30: 2610 + 90 = 2700
Step 31: 2700 + 90 = 2790
Step 32: 2790 + 90 = 2880
Step 33: 2880 + 90 = 2970
Step 34: 2970 + 90 = 3060
Step 35: 3060 + 90 = 3150
Step 36: 3150 + 90 = 3240
Step 37: 3240 + 90 = 3330
Step 38: 3330 + 90 = 3420
Step 39: 3420 + 90 = 3510
Step 40: 3510 + 90 = 3600
Step 41: 3600 + 90 = 3690
Step 42: 3690 + 90 = 3780
Step 43: 3780 + 90 = 3870
Step 44: 3870 + 90 = 3960
Step 45: 3960 + 90 = 4050
Step 46: 4050 + 90 = 4140
Step 47: 4140 + 90 = 4230
Step 48: 4230 + 90 = 4320
Step 49: 4320 + 90 = 4410
Step 50: 4410 + 90 = 4500
Step 51: 4500 + 90 = 4590
Step 52: 4590 + 90 = 4680
Step 53: 4680 + 90 = 4770
Step 54: 4770 + 90 = 4860
Step 55: 4860 + 90 = 4950
Step 56: 4950 + 90 = 5040
Step 57: 5040 + 90 = 5130
Step 58: 5130 + 90 = 5220
Step 59: 5220 + 90 = 5310
Step 60: 5310 + 90 = 5400
Step 61: 5400 + 90 = 5490
Step 62: 5490 + 90 = 5580
Step 63: 5580 + 90 = 5670
Step 64: 5670 + 90 = 5760
Step 65: 5760 + 90 = 5850
Step 66: 5850 + 90 = 5940
Step 67: 5940 + 90 = 6030
Step 68: 6030 + 90 = 6120

So, 90*68 = 6120