Answer:
x = 35
Explanation:
The sum of all three angles is equal to 180 because they make a straight line which is also called a flat angle
3x - 15 + 2x + 10 + 20 = 180 add like terms
5x + 15 = 180 subtract 15 from both sides
5x = 165 divide both sides by 5
x = 33