We are to evaluate the formula 4x + 4
a. when x = 6
substitute the value in the expression and then evaluate
4(6) + 4 = 24 + 4 = 28
b. when x = 9
substitute x = 9 in the expressiona and then evaluate
4(9) + 4 =40
c. when x = 13
substitute x = 13 in the expression and then evaluate
4(13) + 4 = 56