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the denonator is 6 because that is the number of numbers there are, and the numerator is 2 because there are 2 numbers less than or equal to 16. you can simplify
If triangle MNO is congruent to triangle PQR then side OM is congruent to side RP and equals 9
You get everything you need from factoring the last expression:

The left side is a difference of squares, and we get another difference of squares upon factoring. We end up with

Plug in everything you know and solve for
:
