Your friend is adding $3+2$, before multiplying $2(9)$. You should help him by explaining that in the order of operations, multiplication and division come before addition and subtraction. Use the acronym PEMDAS, Parenthesis, Exponents (and Square Roots), Multiplication/Division, and then Addition/Subtraction.
Work Step by Step
Your friend is solving the equation as if it were like the following: $(3+2)(9)$ $(5)(9)$ $45$ He is solving it as it as if you solve from left to right. However, since there is multiplication, that is done before addition. Therefore, the problem should be solved as such: $3+2(9)$ $3+18$ $21$