David spent 25% of his money at the department store. If he had $27.36 left, how much money did he start with

Ascatterplot is produced to compare the size of a school building to the number of students at that school who play an instrument. there are 12 data points, each representing a different school. the points are widely dispersed on the scatterplot without a pattern of grouping. which statement could be true

How do i do this? i don’t understand

If cos(2x) = tan^2(y), show that cos(2y) = tan^2(x).