OK, let's work through this together. We're starting with 721 and we're going to multiply it by 3, which means we add 721 to itself 3 times.
Step 1: 0 + 721 = 721
Step 2: 721 + 721 = 1442
Step 3: 1442 + 721 = 2163

So, 721*3 = 2163