Your car gets 20 miles per gallon of gas. This is 4 more miles per gallon than your friend's car gets. How many miles per gallon does your friend's car get?

Your friend's car gets (20 - 4) = <<20-4=16>>16 miles per gallon. Answer: \boxed{16}.

To find out how many miles per gallon your friend's car gets, we can start by knowing that your car gets 20 miles per gallon of gas.

To figure out how many miles per gallon your friend's car gets, we need to subtract the additional 4 miles per gallon that your car gets.

So, we can subtract 4 from 20:

20 - 4 = 16

Therefore, your friend's car gets 16 miles per gallon.

Let's assume the number of miles per gallon that your friend's car gets is "x".

Given that your car gets 4 more miles per gallon than your friend's car, we can represent this as:

x + 4 = 20

To find the value of "x", we need to isolate it on one side of the equation. Subtracting 4 from both sides of the equation:

x = 20 - 4

x = 16

Therefore, your friend's car gets 16 miles per gallon.