Answer:
3
Explanation:
You want side QR in parallelogram PQRS having side PS marked as 3.
Parallelogram
Opposite sides of a parallelogram are the same length, so ...
QR = PS = 3
The length of QR is 3 units.
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Additional comment
In a parallelogram, opposite sides are parallel and are the same length. Opposite angles have the same measure, and adjacent angles are supplementary. The diagonals bisect each other, but are usually different lengths and usually do not cross at right angles.
(If diagonals are the same length, it is a rectangle; if they cross at right angles, it is a rhombus. A rectangular rhombus is a square.)