Hi!
It says the length of the mural is 15 ft. It also says the height of the mural is 6 ft high. So the first ratio is
15 to 6
The second ratio needs the length of the scale mural, which is 2.5 ft. It also needs the length of the actual mural which we already know is 15.
2.5 to 15
Hope this helps! :)
-Peredhel