Okay so you’re trying to get them to add up to 540 degrees.
On one side of the equation, have this, and on the other, add up your degrees on the shape.
(3x)+(10x-8)+(5x-12)+(120)+(2x)=540
Start by combining like terms on the left side.
20x+100=540
-100 -100
___________
20x=440
—— ——
20 20
x=22
(On this step, I was just solving and isolating the variable.)
Hope this helps!!
