OK, let's work through this together. We're starting with 368 and we're going to multiply it by 21, which means we add 368 to itself 21 times.
Step 1: 0 + 368 = 368
Step 2: 368 + 368 = 736
Step 3: 736 + 368 = 1104
Step 4: 1104 + 368 = 1472
Step 5: 1472 + 368 = 1840
Step 6: 1840 + 368 = 2208
Step 7: 2208 + 368 = 2576
Step 8: 2576 + 368 = 2944
Step 9: 2944 + 368 = 3312
Step 10: 3312 + 368 = 3680
Step 11: 3680 + 368 = 4048
Step 12: 4048 + 368 = 4416
Step 13: 4416 + 368 = 4784
Step 14: 4784 + 368 = 5152
Step 15: 5152 + 368 = 5520
Step 16: 5520 + 368 = 5888
Step 17: 5888 + 368 = 6256
Step 18: 6256 + 368 = 6624
Step 19: 6624 + 368 = 6992
Step 20: 6992 + 368 = 7360
Step 21: 7360 + 368 = 7728

So, 368*21 = 7728