How to simplify 18+3 (9f-13)

(for this answer i'm gonna use 0 to make it easier

firstly you have to reoder the terms like this : 18 + 3 (-13+9f) = 0

then you multiply - 13 and 9f by 3 like this : 18 + (-13 x 3 + 9f x 3) = 0 and it should be like this: 18 + (-39 + 27f) = 0

Next you have to combine like terms which is: 18 + - 39 and you will get - 21 and you add it to 27f which is: - 21 + 27f=0 and you have to solve for the variable f and move all the terms containing f to the left and all other terms to the right.

27f-39+18=27f-21

That is the answer enjoy