Sure thing, let's get straight to it. We start with 503 and we're going to multiply it by 7, which means adding 503 to itself 7 times.
Step 1: 0 + 503 = 503
Step 2: 503 + 503 = 1006
Step 3: 1006 + 503 = 1509
Step 4: 1509 + 503 = 2012
Step 5: 2012 + 503 = 2515
Step 6: 2515 + 503 = 3018
Step 7: 3018 + 503 = 3521

So, 503*7 = 3521