OK, let's work through this together. We're starting with 320 and we're going to multiply it by 7, which means we add 320 to itself 7 times.
Step 1: 0 + 320 = 320
Step 2: 320 + 320 = 640
Step 3: 640 + 320 = 960
Step 4: 960 + 320 = 1280
Step 5: 1280 + 320 = 1600
Step 6: 1600 + 320 = 1920
Step 7: 1920 + 320 = 2240

So, 320*7 = 2240