The entire thing is equal to 180 degrees. so, 100+3x+x=180, which can be simplified to 100+4x=180. If we subtract 100 from both sides, we get 4x=80, 80 divided by 4 is 20, so x=20
What you have to find is LCM(least common multiple in order to find the lcm all you have to do is list all the multiples and find their common multiple.
