Answer:
Step-by-step explanation:
Answer: (21,12)
Step-by-step explanation:
Beacuse <span>A square by definition is a "plane figure having four equal sides." Rectangles' sides are not equal and hence cannot be a square.
A rectangle by definition is a "four-sided plane figure with 4 right angles" - which also implies that a square can be a rectangle because it is also a four-sided plane figure with 4 right angles...... hope this helps</span>
For this case we have the following data:


So that the figure can be a rectangle, its diagonals must be equal, that is, 
In this way we have:

Clearing x we have:


Thus, x must be equal to 10 so that the figure is a rectangle.
Answer:

Option A