OK, let's work through this together. We're starting with 850 and we're going to multiply it by 3, which means we add 850 to itself 3 times.
Step 1: 0 + 850 = 850
Step 2: 850 + 850 = 1700
Step 3: 1700 + 850 = 2550

So, 850*3 = 2550