OK, let's work through this together. We're starting with 870 and we're going to multiply it by 6, which means we add 870 to itself 6 times.
Step 1: 0 + 870 = 870
Step 2: 870 + 870 = 1740
Step 3: 1740 + 870 = 2610
Step 4: 2610 + 870 = 3480
Step 5: 3480 + 870 = 4350
Step 6: 4350 + 870 = 5220

So, 870*6 = 5220