Help. Find the area of the composite shape

Apublic library wants to place 4 magazines and 9 books on each display shelf. the expressions 4s +9s represents the total number of items that will be displayed on s shelves. simplify this expression

Quick translate "x is 12 units from 20" into an equation. what are the values of x being described? if you can answer any of my other questions that'd be great too

Solve the given system of equations. 2y= -x+9 , 3x-6= -15