If bcde is congruent to opqr, then de is congruento to ?

Two shapes are congruent if one of them can become the other using turns, flips and slides. Thus, it will be true that their corresponding angles should have the same measures and that their corresponding sides should have the same lengths.

So, as shown in the figure below we have two quadrilaterals, namely BCDE and OPQR. If we turn this shape counterclockwise then there will be an angle in which the two shapes matches, therefore they are congruent. Given that this is true, then DE is congruent to QR.