Qrst is a parallelogram. find x and y.

In parallelograms, opposite sides are congruent, meaning that they are the same lengths. So, we have:

y - 4x = 9

-x + 4 = y

Add x to both sides of the second equation:

y + x = 4

y - 4x = 9

This is a system of linear equations. Solve by eliminating the y and subtracting the two equations:

5x = -5

x = -1

Use x to solve for y:

y + (-1) = 4

y = 5

So, x = -1 and y = 5.