Let T be the score that Ben obtains in his third game, then, the average of his 3 scores is:
[tex]\frac{137+217+T}{3}\text{.}[/tex]Ben wants the mean to be at least 170, then we can set the following inequality:
[tex]\frac{137+217+T}{3}\ge170.[/tex]Solving the above inequality for T we get:
[tex]\begin{gathered} 137+217+T\ge510, \\ T\ge510-137-217, \\ T\ge156. \end{gathered}[/tex]Answer: Ben has to score at least 156 points in his third game.