Alright, let's solve this math problem step by step. First, we have the number 901. Next, we see the multiplication sign, which means we need to multiply something. And what are we multiplying it by? We multiply it by 15. So, we're going to take the number 901 and add it to itself 15 times.
Step 1: 0 + 901 = 901
Step 2: 901 + 901 = 1802
Step 3: 1802 + 901 = 2703
Step 4: 2703 + 901 = 3604
Step 5: 3604 + 901 = 4505
Step 6: 4505 + 901 = 5406
Step 7: 5406 + 901 = 6307
Step 8: 6307 + 901 = 7208
Step 9: 7208 + 901 = 8109
Step 10: 8109 + 901 = 9010
Step 11: 9010 + 901 = 9911
Step 12: 9911 + 901 = 10812
Step 13: 10812 + 901 = 11713
Step 14: 11713 + 901 = 12614
Step 15: 12614 + 901 = 13515

So, 901*15 = 13515