posted by Jordan .
. Katrina lives directly east of the park. The football field is directly south of the park. The library sits on the line formed between Katrina’s home and the football field at the exact point where an altitude to the right triangle formed by her home, the park, and the football field could be drawn. The library is 4 miles from her home. The football field is 18 miles from the library.
I don't see any question here, but if you label the triangle's vertices as
PKF, with P as the right angle, then the library sits at L, where
∆PKF ~ ∆LFP ~ ∆LKP
You can get the length of PL or FL or KL from those ratios.