OK, let's work through this together. We're starting with 144 and we're going to multiply it by 135, which means we add 144 to itself 135 times.
Step 1: 0 + 144 = 144
Step 2: 144 + 144 = 288
Step 3: 288 + 144 = 432
Step 4: 432 + 144 = 576
Step 5: 576 + 144 = 720
Step 6: 720 + 144 = 864
Step 7: 864 + 144 = 1008
Step 8: 1008 + 144 = 1152
Step 9: 1152 + 144 = 1296
Step 10: 1296 + 144 = 1440
Step 11: 1440 + 144 = 1584
Step 12: 1584 + 144 = 1728
Step 13: 1728 + 144 = 1872
Step 14: 1872 + 144 = 2016
Step 15: 2016 + 144 = 2160
Step 16: 2160 + 144 = 2304
Step 17: 2304 + 144 = 2448
Step 18: 2448 + 144 = 2592
Step 19: 2592 + 144 = 2736
Step 20: 2736 + 144 = 2880
Step 21: 2880 + 144 = 3024
Step 22: 3024 + 144 = 3168
Step 23: 3168 + 144 = 3312
Step 24: 3312 + 144 = 3456
Step 25: 3456 + 144 = 3600
Step 26: 3600 + 144 = 3744
Step 27: 3744 + 144 = 3888
Step 28: 3888 + 144 = 4032
Step 29: 4032 + 144 = 4176
Step 30: 4176 + 144 = 4320
Step 31: 4320 + 144 = 4464
Step 32: 4464 + 144 = 4608
Step 33: 4608 + 144 = 4752
Step 34: 4752 + 144 = 4896
Step 35: 4896 + 144 = 5040
Step 36: 5040 + 144 = 5184
Step 37: 5184 + 144 = 5328
Step 38: 5328 + 144 = 5472
Step 39: 5472 + 144 = 5616
Step 40: 5616 + 144 = 5760
Step 41: 5760 + 144 = 5904
Step 42: 5904 + 144 = 6048
Step 43: 6048 + 144 = 6192
Step 44: 6192 + 144 = 6336
Step 45: 6336 + 144 = 6480
Step 46: 6480 + 144 = 6624
Step 47: 6624 + 144 = 6768
Step 48: 6768 + 144 = 6912
Step 49: 6912 + 144 = 7056
Step 50: 7056 + 144 = 7200
Step 51: 7200 + 144 = 7344
Step 52: 7344 + 144 = 7488
Step 53: 7488 + 144 = 7632
Step 54: 7632 + 144 = 7776
Step 55: 7776 + 144 = 7920
Step 56: 7920 + 144 = 8064
Step 57: 8064 + 144 = 8208
Step 58: 8208 + 144 = 8352
Step 59: 8352 + 144 = 8496
Step 60: 8496 + 144 = 8640
Step 61: 8640 + 144 = 8784
Step 62: 8784 + 144 = 8928
Step 63: 8928 + 144 = 9072
Step 64: 9072 + 144 = 9216
Step 65: 9216 + 144 = 9360
Step 66: 9360 + 144 = 9504
Step 67: 9504 + 144 = 9648
Step 68: 9648 + 144 = 9792
Step 69: 9792 + 144 = 9936
Step 70: 9936 + 144 = 10080
Step 71: 10080 + 144 = 10224
Step 72: 10224 + 144 = 10368
Step 73: 10368 + 144 = 10512
Step 74: 10512 + 144 = 10656
Step 75: 10656 + 144 = 10800
Step 76: 10800 + 144 = 10944
Step 77: 10944 + 144 = 11088
Step 78: 11088 + 144 = 11232
Step 79: 11232 + 144 = 11376
Step 80: 11376 + 144 = 11520
Step 81: 11520 + 144 = 11664
Step 82: 11664 + 144 = 11808
Step 83: 11808 + 144 = 11952
Step 84: 11952 + 144 = 12096
Step 85: 12096 + 144 = 12240
Step 86: 12240 + 144 = 12384
Step 87: 12384 + 144 = 12528
Step 88: 12528 + 144 = 12672
Step 89: 12672 + 144 = 12816
Step 90: 12816 + 144 = 12960
Step 91: 12960 + 144 = 13104
Step 92: 13104 + 144 = 13248
Step 93: 13248 + 144 = 13392
Step 94: 13392 + 144 = 13536
Step 95: 13536 + 144 = 13680
Step 96: 13680 + 144 = 13824
Step 97: 13824 + 144 = 13968
Step 98: 13968 + 144 = 14112
Step 99: 14112 + 144 = 14256
Step 100: 14256 + 144 = 14400
Step 101: 14400 + 144 = 14544
Step 102: 14544 + 144 = 14688
Step 103: 14688 + 144 = 14832
Step 104: 14832 + 144 = 14976
Step 105: 14976 + 144 = 15120
Step 106: 15120 + 144 = 15264
Step 107: 15264 + 144 = 15408
Step 108: 15408 + 144 = 15552
Step 109: 15552 + 144 = 15696
Step 110: 15696 + 144 = 15840
Step 111: 15840 + 144 = 15984
Step 112: 15984 + 144 = 16128
Step 113: 16128 + 144 = 16272
Step 114: 16272 + 144 = 16416
Step 115: 16416 + 144 = 16560
Step 116: 16560 + 144 = 16704
Step 117: 16704 + 144 = 16848
Step 118: 16848 + 144 = 16992
Step 119: 16992 + 144 = 17136
Step 120: 17136 + 144 = 17280
Step 121: 17280 + 144 = 17424
Step 122: 17424 + 144 = 17568
Step 123: 17568 + 144 = 17712
Step 124: 17712 + 144 = 17856
Step 125: 17856 + 144 = 18000
Step 126: 18000 + 144 = 18144
Step 127: 18144 + 144 = 18288
Step 128: 18288 + 144 = 18432
Step 129: 18432 + 144 = 18576
Step 130: 18576 + 144 = 18720
Step 131: 18720 + 144 = 18864
Step 132: 18864 + 144 = 19008
Step 133: 19008 + 144 = 19152
Step 134: 19152 + 144 = 19296
Step 135: 19296 + 144 = 19440

So, 144*135 = 19440