Please I really don't understand it and I thought of C because the line goes down so I really don't know​

Which equation results from adding the equations in this system? x+6y=9 and -x+2y=-15

Which statement explains how you could use coordinate geometry to prove the opposite sides of a quadrilateral are congruent? a. use the slope formula to prove the slopes of the opposite sides are the same. b. use the slope formula to prove the slopes of the opposite sides are opposite reciprocals. c. use the distance formula to prove the lengths of the opposite sides are the same. d. use the distance formula to prove the midpoints of the opposite sides are the same.

What does the quadrilaterals on a kid with her art class it is possible to draw a parallelogram that is not a rectangle explain