OK, let's crack this. We're given 15 and our task is to multiply it by 87. Essentially, we'll be adding 15 to itself 87 times.
Step 1: 0 + 15 = 15
Step 2: 15 + 15 = 30
Step 3: 30 + 15 = 45
Step 4: 45 + 15 = 60
Step 5: 60 + 15 = 75
Step 6: 75 + 15 = 90
Step 7: 90 + 15 = 105
Step 8: 105 + 15 = 120
Step 9: 120 + 15 = 135
Step 10: 135 + 15 = 150
Step 11: 150 + 15 = 165
Step 12: 165 + 15 = 180
Step 13: 180 + 15 = 195
Step 14: 195 + 15 = 210
Step 15: 210 + 15 = 225
Step 16: 225 + 15 = 240
Step 17: 240 + 15 = 255
Step 18: 255 + 15 = 270
Step 19: 270 + 15 = 285
Step 20: 285 + 15 = 300
Step 21: 300 + 15 = 315
Step 22: 315 + 15 = 330
Step 23: 330 + 15 = 345
Step 24: 345 + 15 = 360
Step 25: 360 + 15 = 375
Step 26: 375 + 15 = 390
Step 27: 390 + 15 = 405
Step 28: 405 + 15 = 420
Step 29: 420 + 15 = 435
Step 30: 435 + 15 = 450
Step 31: 450 + 15 = 465
Step 32: 465 + 15 = 480
Step 33: 480 + 15 = 495
Step 34: 495 + 15 = 510
Step 35: 510 + 15 = 525
Step 36: 525 + 15 = 540
Step 37: 540 + 15 = 555
Step 38: 555 + 15 = 570
Step 39: 570 + 15 = 585
Step 40: 585 + 15 = 600
Step 41: 600 + 15 = 615
Step 42: 615 + 15 = 630
Step 43: 630 + 15 = 645
Step 44: 645 + 15 = 660
Step 45: 660 + 15 = 675
Step 46: 675 + 15 = 690
Step 47: 690 + 15 = 705
Step 48: 705 + 15 = 720
Step 49: 720 + 15 = 735
Step 50: 735 + 15 = 750
Step 51: 750 + 15 = 765
Step 52: 765 + 15 = 780
Step 53: 780 + 15 = 795
Step 54: 795 + 15 = 810
Step 55: 810 + 15 = 825
Step 56: 825 + 15 = 840
Step 57: 840 + 15 = 855
Step 58: 855 + 15 = 870
Step 59: 870 + 15 = 885
Step 60: 885 + 15 = 900
Step 61: 900 + 15 = 915
Step 62: 915 + 15 = 930
Step 63: 930 + 15 = 945
Step 64: 945 + 15 = 960
Step 65: 960 + 15 = 975
Step 66: 975 + 15 = 990
Step 67: 990 + 15 = 1005
Step 68: 1005 + 15 = 1020
Step 69: 1020 + 15 = 1035
Step 70: 1035 + 15 = 1050
Step 71: 1050 + 15 = 1065
Step 72: 1065 + 15 = 1080
Step 73: 1080 + 15 = 1095
Step 74: 1095 + 15 = 1110
Step 75: 1110 + 15 = 1125
Step 76: 1125 + 15 = 1140
Step 77: 1140 + 15 = 1155
Step 78: 1155 + 15 = 1170
Step 79: 1170 + 15 = 1185
Step 80: 1185 + 15 = 1200
Step 81: 1200 + 15 = 1215
Step 82: 1215 + 15 = 1230
Step 83: 1230 + 15 = 1245
Step 84: 1245 + 15 = 1260
Step 85: 1260 + 15 = 1275
Step 86: 1275 + 15 = 1290
Step 87: 1290 + 15 = 1305

So, 15*87 = 1305