[tex]\begin{gathered} \text{The correct equation will be given as } \\ \frac{124\text{ + 200 + x}}{3}\text{ }\ge\text{ 170} \\ \text{That is 124 + 200 + x (which is the unknown number he must bowl)} \\ \text{divided by 3 must give us 170 or more. } \end{gathered}[/tex][tex]\begin{gathered} \frac{324\text{ + x}}{3}\text{ }\ge\text{ }\frac{170}{1} \\ \\ \text{Cross multiplying, we have } \\ 324\text{ + x }\ge\text{ 170 x 3} \end{gathered}[/tex][tex]\begin{gathered} 324\text{ + x }\ge\text{ 510} \\ x\text{ }\ge\text{ 510 - 324 } \\ x\text{ }\ge\text{ 186 } \end{gathered}[/tex]
Therefore, Ben must bowl 186 or higher to have an average of at least 170