'a' and 'b' are placeholders for some numbers. In this case, a = 3 and b = 5. So we'll replace every copy of 'a' with 3 and every copy of 'b' with 5. Afterwards, we use PEMDAS to simplify
4(a+2b) = 4*(3+2*5) = 4*(3+10) = 4*(13) = 52
Answer: 52
