Question 781321
You need to know the function f(). For example let
(1) f(x) = x^2 + 3x -4
Then to find f(30), all you do is substitute 30 for every x in the function.
(2) f(30) = 30^2 + 3*30 -4 or
(3) f(30) = 900 + 90 -4 or
(4) f(30) = 986
Does this help? I hope so.