We have to find the inverse of the function: f ( x ) = 1/2 x + 10 y = 1/2 x + 10 - 1/2 x = - y + 10   / * ( - 1 ) 1/2 x = y - 10   / * 2 x = 2 y - 20 f^(-1) ( x )= 2 x  - 20 h ( x ) = 2 x - 20  Answer: The missing value is 20.