OK, let's work through this together. We're starting with 450 and we're going to multiply it by 4, which means we add 450 to itself 4 times.
Step 1: 0 + 450 = 450
Step 2: 450 + 450 = 900
Step 3: 900 + 450 = 1350
Step 4: 1350 + 450 = 1800

So, 450*4 = 1800