SORRY if its too late.
Proportions with variables:
let's look at an example from my homework hehe
.3:4=9:y
First, you change the ratios to fractions.
.3/4=9/y.
4 times 9 is 36. I multiplied the numerator of 9/y and the denominator of .3/4.
You also do this with the other numerators and denominators. .3 times y= 36. (Both equations have to equal the same number) if you don't know the answer, just do 36 divided by .3. The answer is 120.
y=120