.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