as the picture shows, TW is twice RZ, or TW=2(RZ)
if you plug the equations in for the line, you will get:
(5x-20)=2(2x+5)
Then you solve:
5x-20=2(2x+5)
5x-20=4x+10
add 20 to each side
5x-20+20=4x+10+20
5x=4x+30
subtract 4x from each side
5x-4x=4x-4x+30
x=30