The first thing you do is assume a fraction, let's say:
1/2
if the numerator is increased by 60% and its denominator is decreased by 20%, then:
(1(1+60%))/(2*.8)=1.6/1.6=1
So, 1/2 became 1. Let's find out the percentage the fraction increased:
1-(1/2)=1/2=.5
then
(1/2)/1=1/2=.5=50%
Therefore, a fraction will increase by 50%