Will give brainliest if correct : )

I'm so close to finishing all these.

Let f(x) = 3 − x . find the average rate of change of f(x) from x = a to x = a + h and simplify your answer so that no single factor of h is left in the denominator.

Complete the solution of the equation. find the value of y when x equals to 28 x+3y=28