Sure thing, let's get straight to it. We start with 684 and we're going to multiply it by 15, which means adding 684 to itself 15 times.
Step 1: 0 + 684 = 684
Step 2: 684 + 684 = 1368
Step 3: 1368 + 684 = 2052
Step 4: 2052 + 684 = 2736
Step 5: 2736 + 684 = 3420
Step 6: 3420 + 684 = 4104
Step 7: 4104 + 684 = 4788
Step 8: 4788 + 684 = 5472
Step 9: 5472 + 684 = 6156
Step 10: 6156 + 684 = 6840
Step 11: 6840 + 684 = 7524
Step 12: 7524 + 684 = 8208
Step 13: 8208 + 684 = 8892
Step 14: 8892 + 684 = 9576
Step 15: 9576 + 684 = 10260

So, 684*15 = 10260