OK, let's work through this together. We're starting with 435 and we're going to multiply it by 15, which means we add 435 to itself 15 times.
Step 1: 0 + 435 = 435
Step 2: 435 + 435 = 870
Step 3: 870 + 435 = 1305
Step 4: 1305 + 435 = 1740
Step 5: 1740 + 435 = 2175
Step 6: 2175 + 435 = 2610
Step 7: 2610 + 435 = 3045
Step 8: 3045 + 435 = 3480
Step 9: 3480 + 435 = 3915
Step 10: 3915 + 435 = 4350
Step 11: 4350 + 435 = 4785
Step 12: 4785 + 435 = 5220
Step 13: 5220 + 435 = 5655
Step 14: 5655 + 435 = 6090
Step 15: 6090 + 435 = 6525

So, 435*15 = 6525