How about this simply thing ....
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Answer:
RP=16
Step-by-step explanation:
In a parallelogram, the intersection point of the diagonals represents the midpoint of each diagonal. Knowing this, we can say that RS=SP.
If RS=8, then SP=8.
RP is equal to RS + SP, and 8+8 is 16.
I hope this helps! Please comment if you have any questions :)