Mathematics Homework Help

Mathematics Homework Help. Would I add PT and RT together or is there a specific equation

I have a parallelogram that has two intersecting lines coming from the edges. T is the variable where the lines intersect. R and P are in opposite corners of the parallelogram and RT is 19.8. I know this means the PT is 19.8. i need to find what RP is 

Mathematics Homework Help

 
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