Alright, let's solve this math problem step by step. First, we have the number 138. Next, we see the multiplication sign, which means we need to multiply something. And what are we multiplying it by? We multiply it by 87. So, we're going to take the number 138 and add it to itself 87 times.
Step 1: 0 + 138 = 138
Step 2: 138 + 138 = 276
Step 3: 276 + 138 = 414
Step 4: 414 + 138 = 552
Step 5: 552 + 138 = 690
Step 6: 690 + 138 = 828
Step 7: 828 + 138 = 966
Step 8: 966 + 138 = 1104
Step 9: 1104 + 138 = 1242
Step 10: 1242 + 138 = 1380
Step 11: 1380 + 138 = 1518
Step 12: 1518 + 138 = 1656
Step 13: 1656 + 138 = 1794
Step 14: 1794 + 138 = 1932
Step 15: 1932 + 138 = 2070
Step 16: 2070 + 138 = 2208
Step 17: 2208 + 138 = 2346
Step 18: 2346 + 138 = 2484
Step 19: 2484 + 138 = 2622
Step 20: 2622 + 138 = 2760
Step 21: 2760 + 138 = 2898
Step 22: 2898 + 138 = 3036
Step 23: 3036 + 138 = 3174
Step 24: 3174 + 138 = 3312
Step 25: 3312 + 138 = 3450
Step 26: 3450 + 138 = 3588
Step 27: 3588 + 138 = 3726
Step 28: 3726 + 138 = 3864
Step 29: 3864 + 138 = 4002
Step 30: 4002 + 138 = 4140
Step 31: 4140 + 138 = 4278
Step 32: 4278 + 138 = 4416
Step 33: 4416 + 138 = 4554
Step 34: 4554 + 138 = 4692
Step 35: 4692 + 138 = 4830
Step 36: 4830 + 138 = 4968
Step 37: 4968 + 138 = 5106
Step 38: 5106 + 138 = 5244
Step 39: 5244 + 138 = 5382
Step 40: 5382 + 138 = 5520
Step 41: 5520 + 138 = 5658
Step 42: 5658 + 138 = 5796
Step 43: 5796 + 138 = 5934
Step 44: 5934 + 138 = 6072
Step 45: 6072 + 138 = 6210
Step 46: 6210 + 138 = 6348
Step 47: 6348 + 138 = 6486
Step 48: 6486 + 138 = 6624
Step 49: 6624 + 138 = 6762
Step 50: 6762 + 138 = 6900
Step 51: 6900 + 138 = 7038
Step 52: 7038 + 138 = 7176
Step 53: 7176 + 138 = 7314
Step 54: 7314 + 138 = 7452
Step 55: 7452 + 138 = 7590
Step 56: 7590 + 138 = 7728
Step 57: 7728 + 138 = 7866
Step 58: 7866 + 138 = 8004
Step 59: 8004 + 138 = 8142
Step 60: 8142 + 138 = 8280
Step 61: 8280 + 138 = 8418
Step 62: 8418 + 138 = 8556
Step 63: 8556 + 138 = 8694
Step 64: 8694 + 138 = 8832
Step 65: 8832 + 138 = 8970
Step 66: 8970 + 138 = 9108
Step 67: 9108 + 138 = 9246
Step 68: 9246 + 138 = 9384
Step 69: 9384 + 138 = 9522
Step 70: 9522 + 138 = 9660
Step 71: 9660 + 138 = 9798
Step 72: 9798 + 138 = 9936
Step 73: 9936 + 138 = 10074
Step 74: 10074 + 138 = 10212
Step 75: 10212 + 138 = 10350
Step 76: 10350 + 138 = 10488
Step 77: 10488 + 138 = 10626
Step 78: 10626 + 138 = 10764
Step 79: 10764 + 138 = 10902
Step 80: 10902 + 138 = 11040
Step 81: 11040 + 138 = 11178
Step 82: 11178 + 138 = 11316
Step 83: 11316 + 138 = 11454
Step 84: 11454 + 138 = 11592
Step 85: 11592 + 138 = 11730
Step 86: 11730 + 138 = 11868
Step 87: 11868 + 138 = 12006

So, 138*87 = 12006