OK, let's work through this together. We're starting with 720 and we're going to multiply it by 4, which means we add 720 to itself 4 times.
Step 1: 0 + 720 = 720
Step 2: 720 + 720 = 1440
Step 3: 1440 + 720 = 2160
Step 4: 2160 + 720 = 2880

So, 720*4 = 2880