The answer you are looking for is x=34. 
Solution/Explanation: 
 First things first, we need to understand that the sum of the angles of a triangle is 180°. We can apply this fact for the problem. 
 So, that means that the sum of all of the angles of this triangle is 180°. 
 So, therefore, we can formulate an equation: 
 2x+20+2x-10+x=180. 
 So, we now have our expression. 
 Now, all we need to do is simplify it. 
 Combining similar-like terms, 
 2x+2x+x+20-10=180. 
 Simplifying it now, 
 5x+10=180. 
 Subtracting 10 from both sides of the equation, 
5x+10-10=180-10. 
 5x=170. 
 Finally, dividing both sides by 5, 
 5x/5=170/5. 
 x=34. 
 So, therefore the final answer is x=34. 
 I hope that this has helped you. Enjoy your day, and take care!