Answer:
x = 115
Explanation:
Your working's actually right haha you just need to further evaluate that. The two angles do add up to 180°.
x + x - 50 = 180
2x - 50 = 180
Now, we can shift the (-50) to the right-hand side of the equation so that we can find out how much 2x is worth. (-50) would turn to +50 when it shifts.
2x = 180 + 50
= 230
We can find x now.
x = 230 ÷ 2
x = 115