Since triangle PQR is the medial triangle of triangle MNO, QR is equidistant from NO and KL. Similarly, NO is equidistant from J and KL. Therefore, the altitude (J to QR) of triangle JQR is three times the altitude from P to QR. With the same base, the area of triangle JQR is three times triangle PQR which is 3 times 10, 30.
However, I have a question for you. Since triangle PQR is 10, and based on the information given in the question, I believe that MNO cannot be 20. If you draw out the diagram, it will be clearer that triangle MNO is four times triangle PQR.
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