Answer:
X=40
Explanation:
Important proofs/rules to note: the sum of the angles in a triangle is 180 degrees.
Knowing this, you can set the equation up like this:
(x-10)+(2x-10)+2x=180 ---> Then, simplify it to
5x-20=180 ---> Finally solve for x
180+20=5x -->200=5x --->200/5=x---> x=40
DONE!
P.S. ~ You can also check this by plugging 40 back into x for the original equation and see if it is 180 degrees