I will answer this question to the best of my ability, because you have not provided a value of x to plug in.
UW is always equal to 9x-9 or 9(x-1) whenever x is a real number. By plugging in x, we can get the value. For example, if x was 4, we plug in x, giving us 9*4-9=36-9=27 units or 9(4-1)=9(3)=27 units
Don't forget to include units when you complete your answer!
Hope this helps! I did as much as I could!