Alright, let's solve this math problem step by step. First, we have the number 870. Next, we see the multiplication sign, which means we need to multiply something. And what are we multiplying it by? We multiply it by 11. So, we're going to take the number 870 and add it to itself 11 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
Step 7: 5220 + 870 = 6090
Step 8: 6090 + 870 = 6960
Step 9: 6960 + 870 = 7830
Step 10: 7830 + 870 = 8700
Step 11: 8700 + 870 = 9570

So, 870*11 = 9570