Alright, let's solve this math problem step by step. First, we have the number 904. Next, we see the multiplication sign, which means we need to multiply something. And what are we multiplying it by? We multiply it by 90. So, we're going to take the number 904 and add it to itself 90 times.
Step 1: 0 + 904 = 904
Step 2: 904 + 904 = 1808
Step 3: 1808 + 904 = 2712
Step 4: 2712 + 904 = 3616
Step 5: 3616 + 904 = 4520
Step 6: 4520 + 904 = 5424
Step 7: 5424 + 904 = 6328
Step 8: 6328 + 904 = 7232
Step 9: 7232 + 904 = 8136
Step 10: 8136 + 904 = 9040
Step 11: 9040 + 904 = 9944
Step 12: 9944 + 904 = 10848
Step 13: 10848 + 904 = 11752
Step 14: 11752 + 904 = 12656
Step 15: 12656 + 904 = 13560
Step 16: 13560 + 904 = 14464
Step 17: 14464 + 904 = 15368
Step 18: 15368 + 904 = 16272
Step 19: 16272 + 904 = 17176
Step 20: 17176 + 904 = 18080
Step 21: 18080 + 904 = 18984
Step 22: 18984 + 904 = 19888
Step 23: 19888 + 904 = 20792
Step 24: 20792 + 904 = 21696
Step 25: 21696 + 904 = 22600
Step 26: 22600 + 904 = 23504
Step 27: 23504 + 904 = 24408
Step 28: 24408 + 904 = 25312
Step 29: 25312 + 904 = 26216
Step 30: 26216 + 904 = 27120
Step 31: 27120 + 904 = 28024
Step 32: 28024 + 904 = 28928
Step 33: 28928 + 904 = 29832
Step 34: 29832 + 904 = 30736
Step 35: 30736 + 904 = 31640
Step 36: 31640 + 904 = 32544
Step 37: 32544 + 904 = 33448
Step 38: 33448 + 904 = 34352
Step 39: 34352 + 904 = 35256
Step 40: 35256 + 904 = 36160
Step 41: 36160 + 904 = 37064
Step 42: 37064 + 904 = 37968
Step 43: 37968 + 904 = 38872
Step 44: 38872 + 904 = 39776
Step 45: 39776 + 904 = 40680
Step 46: 40680 + 904 = 41584
Step 47: 41584 + 904 = 42488
Step 48: 42488 + 904 = 43392
Step 49: 43392 + 904 = 44296
Step 50: 44296 + 904 = 45200
Step 51: 45200 + 904 = 46104
Step 52: 46104 + 904 = 47008
Step 53: 47008 + 904 = 47912
Step 54: 47912 + 904 = 48816
Step 55: 48816 + 904 = 49720
Step 56: 49720 + 904 = 50624
Step 57: 50624 + 904 = 51528
Step 58: 51528 + 904 = 52432
Step 59: 52432 + 904 = 53336
Step 60: 53336 + 904 = 54240
Step 61: 54240 + 904 = 55144
Step 62: 55144 + 904 = 56048
Step 63: 56048 + 904 = 56952
Step 64: 56952 + 904 = 57856
Step 65: 57856 + 904 = 58760
Step 66: 58760 + 904 = 59664
Step 67: 59664 + 904 = 60568
Step 68: 60568 + 904 = 61472
Step 69: 61472 + 904 = 62376
Step 70: 62376 + 904 = 63280
Step 71: 63280 + 904 = 64184
Step 72: 64184 + 904 = 65088
Step 73: 65088 + 904 = 65992
Step 74: 65992 + 904 = 66896
Step 75: 66896 + 904 = 67800
Step 76: 67800 + 904 = 68704
Step 77: 68704 + 904 = 69608
Step 78: 69608 + 904 = 70512
Step 79: 70512 + 904 = 71416
Step 80: 71416 + 904 = 72320
Step 81: 72320 + 904 = 73224
Step 82: 73224 + 904 = 74128
Step 83: 74128 + 904 = 75032
Step 84: 75032 + 904 = 75936
Step 85: 75936 + 904 = 76840
Step 86: 76840 + 904 = 77744
Step 87: 77744 + 904 = 78648
Step 88: 78648 + 904 = 79552
Step 89: 79552 + 904 = 80456
Step 90: 80456 + 904 = 81360

So, 904*90 = 81360