Let's roll up our sleeves and solve this. We have 520 and we're going to multiply it by 7, essentially adding 520 to itself 7 times.
Step 1: 0 + 520 = 520
Step 2: 520 + 520 = 1040
Step 3: 1040 + 520 = 1560
Step 4: 1560 + 520 = 2080
Step 5: 2080 + 520 = 2600
Step 6: 2600 + 520 = 3120
Step 7: 3120 + 520 = 3640

So, 520*7 = 3640