Notice that we're looking at a set of similar triangles, we can say that:
![RS\parallel QP](https://img.qammunity.org/2023/formulas/mathematics/college/onrgobipiw3vs0lf9bs0cwwt1tck5jfcdb.png)
Now, since RS is parallel to the base of the big triangle, and also connects segments QT and PT by their midpoints, we can say that
![QP=2RS](https://img.qammunity.org/2023/formulas/mathematics/college/t105d6uhru1y8kg2m10pn6ssb425g09s73.png)
Therefore, if QP = 16, then RS = 8 ; and if RS = 9 , then QP = 18