When a question says use subtitution to decide if x=... ? Take the equation and put a (...) in place of all x's. In the given equation this would be; 5((-2)+4)-3((-2)+6)=9((-2)+1). Now you just process. 5(2)-3(4)=9(-1) 10-12=-9 -2=-9. NO! -2≠-9. Therefore x≠2 Basically this process is a "try it and see if it's true" process.