9514 1404 393
Step-by-step explanation:
The figure will be a rectangle only if the angles between adjacent congruent sides are 90°.
__
Attached is an example of a quadrilateral with 3 congruent sides. It is not a rectangle, but could be an isosceles trapezoid if the top and bottom sides were parallel. It would be a parallelogram (rhombus) if opposite congruent sides were parallel.