The rectangular prism shown has a surface area of 426 square inches. the height is 9, the width is 5, the length is unknown. what is the length of the prism

The surface area of a rectangular prism is:

A=2 (LW+LH+WH)

LW+LH+WH=A/2

LW+LH = (A/2) - WH

L (W+H) = [ (A/2) - WH]

L=[ (A/2) - WH] / (W+H), we are told that A=426, H=9, and W=5 so:

L = (426/2-5*9) / (5+9)

L = (213-45) / (14)

L=168/14

L=12 in