OK, let's work through this together. We're starting with 907 and we're going to multiply it by 3, which means we add 907 to itself 3 times.
Step 1: 0 + 907 = 907
Step 2: 907 + 907 = 1814
Step 3: 1814 + 907 = 2721

So, 907*3 = 2721