The angle on the left (x+15) and the angle on the right (4x-20) put together would have to equal 180 since a straight like is 180 degrees. If you add like terms the problem would be 5x-5=180. You would have to add 5 (since its negative in the problem) to 180, making the problem 5x=185. Now you divide by 5 (since it's multiplied by 'x') by both sides, which makes your answer x=37
