Could you please explain the answers to both questions? Thanks!

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

Eis the midpoint of line segment ac and bd also line segment ed is congruent to ec prove that line segment ae is congruent to line segment be

Find the equation of a line that is perpendicular to line g that contains (p, q). coordinate plane with line g that passes through the points negative 3 comma 6 and 0 comma 5 3x − y = 3p − q 3x + y = q − 3p x − y = p − q x + y = q − p