Let's roll up our sleeves and solve this. We have 804 and we're going to multiply it by 13, essentially adding 804 to itself 13 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

So, 804*13 = 10452