I don't understand how to work this problem. Could someone please help?

Suppose https://webwork.math.lsu.edu/webwork...ccbd6d5d01.png and https://webwork.math.lsu.edu/webwork...9844d76111.png. Find https://webwork.math.lsu.edu/webwork...b28c727511.png when https://webwork.math.lsu.edu/webwork...7c200b8dd1.png.

https://webwork.math.lsu.edu/webwork...b28c727511.png =