Let's get this math done. We have 871 and we're going to multiply it by 12. This is the same as taking 871 and adding it to itself 12 times.
Step 1: 0 + 871 = 871
Step 2: 871 + 871 = 1742
Step 3: 1742 + 871 = 2613
Step 4: 2613 + 871 = 3484
Step 5: 3484 + 871 = 4355
Step 6: 4355 + 871 = 5226
Step 7: 5226 + 871 = 6097
Step 8: 6097 + 871 = 6968
Step 9: 6968 + 871 = 7839
Step 10: 7839 + 871 = 8710
Step 11: 8710 + 871 = 9581
Step 12: 9581 + 871 = 10452

So, 871*12 = 10452