Sure thing, let's get straight to it. We start with 400 and we're going to multiply it by 7, which means adding 400 to itself 7 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

So, 400*7 = 2800