OK, let's work through this together. We're starting with 668 and we're going to multiply it by 9, which means we add 668 to itself 9 times.
Step 1: 0 + 668 = 668
Step 2: 668 + 668 = 1336
Step 3: 1336 + 668 = 2004
Step 4: 2004 + 668 = 2672
Step 5: 2672 + 668 = 3340
Step 6: 3340 + 668 = 4008
Step 7: 4008 + 668 = 4676
Step 8: 4676 + 668 = 5344
Step 9: 5344 + 668 = 6012

So, 668*9 = 6012