Question

I don't understand how to do this.

Answer 1

If QS bisects PQR and RQS = 71, PQS=RQS and PQR=2RQS.
Therefore, PQS = 71 and PQR = 142

Answer 2

QS bisects PQR. This means, basically, that QS cuts PQR exactly in half.

Therefore, RQS = PQS

We know that RQS = 71. So PQS also equals 71.

RQS is HALF of PQR. So, if RQS = 71, then PQR = 142

PQS = 71

PQR = 142

Let me know if you have any questions about this!