We have the equation f(x)=6x-5 to start with
Now in order to answer the question we have to know that f(5) is the same thing as setting x=5 and solving for f(5)
(A) f(5) = 6(5) - 5 = 30 - 5 = 25
(B) f(-3) = 6(-3) - 5 = (-18) - 5 = -23
So f(5) = 25 and f(-3) = -23