If y=15 when x=3/4, then y=5 when x=1/4 because 15 and 3/4 are both divisible by 3. We have to find x when y=25, and 25 is divisible by 5, so to find x you have to multiply y=5 and x=1 by 5 for y to equal 25. 5 times 5 equals 25, and 1 times 5 equals 5, so when y=25, x=5.
