ABCD is a parallelogram. Find the values of x and y. Solve for the value of z, if z=x−y.
A. -10
B. -20
C. 20
D. 30

Answer:
C
Step-by-step explanation:
Parallel and opposite sides of a parallelogram are equal. Hence, we can say:
x + 30 = 2x - 10
and
2y-10 = y +10
Solving first one, we get:
x + 30 = 2x - 10
30+10 = x
x = 40
Also
2y - 10 = y + 10
y = 10 + 10
y = 20
Now, z = x - y, so
z = 40 - 20 = 20
Answer C is right.
I can confirm that the answer is right.
Parallelograms have equal opposite sides. Do the math:
x - y = z
40 - 20 = 20
z = 20