Let's roll up our sleeves and solve this. We have 790 and we're going to multiply it by 4, essentially adding 790 to itself 4 times.
Step 1: 0 + 790 = 790
Step 2: 790 + 790 = 1580
Step 3: 1580 + 790 = 2370
Step 4: 2370 + 790 = 3160

So, 790*4 = 3160