please zoom in on the pic and answer all of them with proper calculations will mark brainlist if correct answers

Perform the required operations on the following functions given: f(x)= 3-x; g(x)= -2x find g[f(x)]

Cindy uses 1-inch cubes to find the volume of a jewelry box shaped like a rectangular prism. she uses 780 cubes to completely fill the jewelry box with no gaps or overlaps. if the jewelry box is 13 inches long and 5 inches wide, how tall is cindy’s jewelry box?

Which expression is equivalent to7_/x^2 ÷ 5_/y^3? assume y# 0