OK, let's work through this together. We're starting with 909 and we're going to multiply it by 9, which means we add 909 to itself 9 times.
Step 1: 0 + 909 = 909
Step 2: 909 + 909 = 1818
Step 3: 1818 + 909 = 2727
Step 4: 2727 + 909 = 3636
Step 5: 3636 + 909 = 4545
Step 6: 4545 + 909 = 5454
Step 7: 5454 + 909 = 6363
Step 8: 6363 + 909 = 7272
Step 9: 7272 + 909 = 8181

So, 909*9 = 8181