when I put in the -2 in for the x and I submit, it tells me it's wrong

Evaluate the function f at the indicated values. 6x - 5 f ( 20 ) = 2 + 3 a. f( -2) = b. f (3) =[ c. f (-a) = answer (Your answer should be in terms of a.) d. - f(a) = (Your answer should be in terms of a.) e. flat h) = (Your answer should be in terms of a and h. Be sure to simplify us