Alright, let's solve this math problem step by step. First, we have the number 13. Next, we see the multiplication sign, which means we need to multiply something. And what are we multiplying it by? We multiply it by 99. So, we're going to take the number 13 and add it to itself 99 times.
Step 1: 0 + 13 = 13
Step 2: 13 + 13 = 26
Step 3: 26 + 13 = 39
Step 4: 39 + 13 = 52
Step 5: 52 + 13 = 65
Step 6: 65 + 13 = 78
Step 7: 78 + 13 = 91
Step 8: 91 + 13 = 104
Step 9: 104 + 13 = 117
Step 10: 117 + 13 = 130
Step 11: 130 + 13 = 143
Step 12: 143 + 13 = 156
Step 13: 156 + 13 = 169
Step 14: 169 + 13 = 182
Step 15: 182 + 13 = 195
Step 16: 195 + 13 = 208
Step 17: 208 + 13 = 221
Step 18: 221 + 13 = 234
Step 19: 234 + 13 = 247
Step 20: 247 + 13 = 260
Step 21: 260 + 13 = 273
Step 22: 273 + 13 = 286
Step 23: 286 + 13 = 299
Step 24: 299 + 13 = 312
Step 25: 312 + 13 = 325
Step 26: 325 + 13 = 338
Step 27: 338 + 13 = 351
Step 28: 351 + 13 = 364
Step 29: 364 + 13 = 377
Step 30: 377 + 13 = 390
Step 31: 390 + 13 = 403
Step 32: 403 + 13 = 416
Step 33: 416 + 13 = 429
Step 34: 429 + 13 = 442
Step 35: 442 + 13 = 455
Step 36: 455 + 13 = 468
Step 37: 468 + 13 = 481
Step 38: 481 + 13 = 494
Step 39: 494 + 13 = 507
Step 40: 507 + 13 = 520
Step 41: 520 + 13 = 533
Step 42: 533 + 13 = 546
Step 43: 546 + 13 = 559
Step 44: 559 + 13 = 572
Step 45: 572 + 13 = 585
Step 46: 585 + 13 = 598
Step 47: 598 + 13 = 611
Step 48: 611 + 13 = 624
Step 49: 624 + 13 = 637
Step 50: 637 + 13 = 650
Step 51: 650 + 13 = 663
Step 52: 663 + 13 = 676
Step 53: 676 + 13 = 689
Step 54: 689 + 13 = 702
Step 55: 702 + 13 = 715
Step 56: 715 + 13 = 728
Step 57: 728 + 13 = 741
Step 58: 741 + 13 = 754
Step 59: 754 + 13 = 767
Step 60: 767 + 13 = 780
Step 61: 780 + 13 = 793
Step 62: 793 + 13 = 806
Step 63: 806 + 13 = 819
Step 64: 819 + 13 = 832
Step 65: 832 + 13 = 845
Step 66: 845 + 13 = 858
Step 67: 858 + 13 = 871
Step 68: 871 + 13 = 884
Step 69: 884 + 13 = 897
Step 70: 897 + 13 = 910
Step 71: 910 + 13 = 923
Step 72: 923 + 13 = 936
Step 73: 936 + 13 = 949
Step 74: 949 + 13 = 962
Step 75: 962 + 13 = 975
Step 76: 975 + 13 = 988
Step 77: 988 + 13 = 1001
Step 78: 1001 + 13 = 1014
Step 79: 1014 + 13 = 1027
Step 80: 1027 + 13 = 1040
Step 81: 1040 + 13 = 1053
Step 82: 1053 + 13 = 1066
Step 83: 1066 + 13 = 1079
Step 84: 1079 + 13 = 1092
Step 85: 1092 + 13 = 1105
Step 86: 1105 + 13 = 1118
Step 87: 1118 + 13 = 1131
Step 88: 1131 + 13 = 1144
Step 89: 1144 + 13 = 1157
Step 90: 1157 + 13 = 1170
Step 91: 1170 + 13 = 1183
Step 92: 1183 + 13 = 1196
Step 93: 1196 + 13 = 1209
Step 94: 1209 + 13 = 1222
Step 95: 1222 + 13 = 1235
Step 96: 1235 + 13 = 1248
Step 97: 1248 + 13 = 1261
Step 98: 1261 + 13 = 1274
Step 99: 1274 + 13 = 1287

So, 13*99 = 1287