Ratio tablesi do not understand it ne

Which expression is equivalent to 8(k + m) − 15(2k + 5m)?

This stem-and-leaf plot represents the heights of the students on ralph's basketball team. one student's height is missing from the plot. if the mean height of all the students on the team is 61 inches, what is the missing height? a. 55 in. b. 59 in. c. 61 in. d. 65 in.

Asap! i'm not good math and i'm lost.