



 
Hi Barbara, I am not sure I have the diagram correct but here is my interpretation of what you sent. The large triangle is PST and the small triangle is PQR. If QR is parallel to ST then the triangles PQR and PST are similar. This means, in particular, that the ratios of the lengths of the corresponding sides is the same. that is
Since (length QR)/(length ST) = 17/34 = 1/2 you can conclude that PQ is half as long as PS and RP is half as long as TP. I hope this helps,  


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