Answer:
2.5cm
Explanation:
The shapes are similar and so have a scale-factor. We can find the scale-factor by dividing one of the lengths that we know on the bigger shape by the corresponding side on the smaller shape.
For example: PQ/LM = 6/3 = 2
Now that we know to get from the larger shape to the smaller shape, we have to multiply by 2. We can use this scale factor to find the length of the side MN.
QR = MN x 2
MN = QR/2 = 5/2 = 2.5cm