Sure thing, let's get straight to it. We start with 990 and we're going to multiply it by 10, which means adding 990 to itself 10 times.
Step 1: 0 + 990 = 990
Step 2: 990 + 990 = 1980
Step 3: 1980 + 990 = 2970
Step 4: 2970 + 990 = 3960
Step 5: 3960 + 990 = 4950
Step 6: 4950 + 990 = 5940
Step 7: 5940 + 990 = 6930
Step 8: 6930 + 990 = 7920
Step 9: 7920 + 990 = 8910
Step 10: 8910 + 990 = 9900

So, 990*10 = 9900