How do I know which answer to use? Evaluate the piecewise function at the given value of the ind. variable?

well it tells you in the piecewise part. the if part has to be true for the function to be right. so f(-6) is saying -6 is x. and -6 is less than or equal to -4 so you have to use that one. if it were say for example f(6) then 6>4 so you wouldve used the first one