OK, let's work through this together. We're starting with 663 and we're going to multiply it by 18, which means we add 663 to itself 18 times.
Step 1: 0 + 663 = 663
Step 2: 663 + 663 = 1326
Step 3: 1326 + 663 = 1989
Step 4: 1989 + 663 = 2652
Step 5: 2652 + 663 = 3315
Step 6: 3315 + 663 = 3978
Step 7: 3978 + 663 = 4641
Step 8: 4641 + 663 = 5304
Step 9: 5304 + 663 = 5967
Step 10: 5967 + 663 = 6630
Step 11: 6630 + 663 = 7293
Step 12: 7293 + 663 = 7956
Step 13: 7956 + 663 = 8619
Step 14: 8619 + 663 = 9282
Step 15: 9282 + 663 = 9945
Step 16: 9945 + 663 = 10608
Step 17: 10608 + 663 = 11271
Step 18: 11271 + 663 = 11934

So, 663*18 = 11934