Sure thing! We've got 804 and we're gonna multiply it by 40. That's the same as adding 804 to itself 40 times.
Step 1: 0 + 804 = 804
Step 2: 804 + 804 = 1608
Step 3: 1608 + 804 = 2412
Step 4: 2412 + 804 = 3216
Step 5: 3216 + 804 = 4020
Step 6: 4020 + 804 = 4824
Step 7: 4824 + 804 = 5628
Step 8: 5628 + 804 = 6432
Step 9: 6432 + 804 = 7236
Step 10: 7236 + 804 = 8040
Step 11: 8040 + 804 = 8844
Step 12: 8844 + 804 = 9648
Step 13: 9648 + 804 = 10452
Step 14: 10452 + 804 = 11256
Step 15: 11256 + 804 = 12060
Step 16: 12060 + 804 = 12864
Step 17: 12864 + 804 = 13668
Step 18: 13668 + 804 = 14472
Step 19: 14472 + 804 = 15276
Step 20: 15276 + 804 = 16080
Step 21: 16080 + 804 = 16884
Step 22: 16884 + 804 = 17688
Step 23: 17688 + 804 = 18492
Step 24: 18492 + 804 = 19296
Step 25: 19296 + 804 = 20100
Step 26: 20100 + 804 = 20904
Step 27: 20904 + 804 = 21708
Step 28: 21708 + 804 = 22512
Step 29: 22512 + 804 = 23316
Step 30: 23316 + 804 = 24120
Step 31: 24120 + 804 = 24924
Step 32: 24924 + 804 = 25728
Step 33: 25728 + 804 = 26532
Step 34: 26532 + 804 = 27336
Step 35: 27336 + 804 = 28140
Step 36: 28140 + 804 = 28944
Step 37: 28944 + 804 = 29748
Step 38: 29748 + 804 = 30552
Step 39: 30552 + 804 = 31356
Step 40: 31356 + 804 = 32160

So, 804*40 = 32160