Having trouble with proving lines parallel on this page. ?

For #1. Step 1: Set the equations equal to one another: (3x + 20) = (2x + 40)

Step 2: Subtract 2x on both sides of the equal sign: (3x-2x + 20) = (2x-2x + 40)

x + 20=40

Step 3: Subtract 20 on both sides of the equal sign: x + 20-20= 40-20

x=20

Step 4: plug in 20 for x: 3(20) + 20= 80 & 2(20) + 40= 80