one way is to find ones or factors
example 4/2=2/2 times 2/1=1 times 2/1
then we undistribute the factor
we want a factor of 3x to make a one
60x=3x times 20
-3x^2=3x tiimes -x
use undistributive property which is
ab+ac=a(b+c)
so
60x-3x=3x(20)+3x(-x)=3x(20-x)
so now we have
[3x(20-x)]/3x=(3x/3x) times (20-x)/1=1 times 20-x=20-x
answer is 20-x