W (x) = 3x; find (-3x)

So this means W (-3x) = 3x. So it's equal to 3 (-3x), which simplifies to be - 9x. Whenever you have a function, it looks like f (x). f doesn't have to be the letter, it can be a, b, c, or like in this case, W. It just means the output of what W (x) is if x equals the number in the parentheses, which is - 3x in this case.