Answer:
x = 21/5
Step-by-step explanation:
Setup a proportion where x -- the short side -- corresponds to 7, and 9 -- the long side -- corresponds with 15. That would look something like x/9 = 7/15. Cross multiply and you get 15x = 63. Divide both sides by 15, and you get x = 63/15 or 21/5.
