The answer is 21
21x3=63 and 21x4=84
Answer:There are three special kinds of parallelograms. A rectangle is a quadrilateral because it has four sides, and it is a parallelogram because it has two pairs of parallel, congruent sides. All four angles are right angles
Step-by-step explanation:
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Answer:

Step-by-step explanation:
Given
Represent the number with x.
So:

or

We want to solve for x
Subtract both sides by 2


Solve for x


No other number aside 0, satisfy the property.
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