OK, let's work through this together. We're starting with 804 and we're going to multiply it by 10, which means we add 804 to itself 10 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

So, 804*10 = 8040