OK, let's work through this together. We're starting with 400 and we're going to multiply it by 17, which means we add 400 to itself 17 times.
Step 1: 0 + 400 = 400
Step 2: 400 + 400 = 800
Step 3: 800 + 400 = 1200
Step 4: 1200 + 400 = 1600
Step 5: 1600 + 400 = 2000
Step 6: 2000 + 400 = 2400
Step 7: 2400 + 400 = 2800
Step 8: 2800 + 400 = 3200
Step 9: 3200 + 400 = 3600
Step 10: 3600 + 400 = 4000
Step 11: 4000 + 400 = 4400
Step 12: 4400 + 400 = 4800
Step 13: 4800 + 400 = 5200
Step 14: 5200 + 400 = 5600
Step 15: 5600 + 400 = 6000
Step 16: 6000 + 400 = 6400
Step 17: 6400 + 400 = 6800

So, 400*17 = 6800