Alright, let's solve this math problem step by step. First, we have the number 15. Next, we see the multiplication sign, which means we need to multiply something. And what are we multiplying it by? We multiply it by 91. So, we're going to take the number 15 and add it to itself 91 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
Step 88: 1305 + 15 = 1320
Step 89: 1320 + 15 = 1335
Step 90: 1335 + 15 = 1350
Step 91: 1350 + 15 = 1365

So, 15*91 = 1365