Find the midpoint between the points (-1, 16) and (-9,-2)

Adj has a total of 1075 dance and rock songs on her system. the dance selection is 4 times the size of the rock selection. write a system of equations to represent the situation.

Select the margin of error that corresponds to the sample mean that corresponds to each population: a population mean of 25, a standard deviation of 2.5, and margin of error of 5%

I'm confused on this could anyone me and show me what i need to do to solve it.