OK, let's work through this together. We're starting with 456 and we're going to multiply it by 3, which means we add 456 to itself 3 times.
Step 1: 0 + 456 = 456
Step 2: 456 + 456 = 912
Step 3: 912 + 456 = 1368

So, 456*3 = 1368