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

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.

not only in mathematics, scientific proof also are required in the other field of science. also maths proofs are of particular structure, containing steps and logics. so proving is like doing science, it is science. that's why it is important to prove. 

an inaccurate proof leads to errors, or stating results that are not accurate.  which wil mess the probelm up you dont want this