Let's roll up our sleeves and solve this. We have 587 and we're going to multiply it by 15, essentially adding 587 to itself 15 times.
Step 1: 0 + 587 = 587
Step 2: 587 + 587 = 1174
Step 3: 1174 + 587 = 1761
Step 4: 1761 + 587 = 2348
Step 5: 2348 + 587 = 2935
Step 6: 2935 + 587 = 3522
Step 7: 3522 + 587 = 4109
Step 8: 4109 + 587 = 4696
Step 9: 4696 + 587 = 5283
Step 10: 5283 + 587 = 5870
Step 11: 5870 + 587 = 6457
Step 12: 6457 + 587 = 7044
Step 13: 7044 + 587 = 7631
Step 14: 7631 + 587 = 8218
Step 15: 8218 + 587 = 8805

So, 587*15 = 8805