I need help how do I solve for x?

Solve the system of equations. y= 2x y= x^2 - 15

Set $r$ is a set of rectangles such that (1) only the grid points shown here are used as vertices, (2) all sides are vertical or horizontal and (3) no two rectangles in the set are congruent. if $r$ contains the maximum possible number of rectangles given these conditions, what fraction of the rectangles in set $r$ are squares? express your answer as a common fraction.

Two years ago a man was six times as old as his daughter. in 18 years he will be twice as old as his daughter. determine their present ages.