Can someone please help me with this I’m very confused
2 answers:
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15. The left triangle is similar to the whole triangle. The x of the small triangle is proportional to the hypotenuse of the large triangle (9+16 =25). the x of the large triangle is proportional to the 9 unit leg of the small triangle. this creates the proportion 
. Cross multiply to get 
take the square roots of both sides to get x=225