Hi there! The answer is B.
The sum of the angles in a triangle is always 180°.
We can also express the sum of the angles in terms of y. The sum will be:
![2y + y + 10 + 50](https://img.qammunity.org/2019/formulas/mathematics/high-school/64wqzepea5un9lci5t825mqdjxwbv848kw.png)
Collect the terms.
![3y + 60](https://img.qammunity.org/2019/formulas/mathematics/high-school/6hzgd7yry533epmwjhnnuqjd190bhh9l73.png)
We can now set up and solve an equation.
![3y + 60 = 180](https://img.qammunity.org/2019/formulas/mathematics/high-school/7t8ao2y2upl05oizl1uizava58kftg1zmd.png)
Subtract 60 from both sides.
![3y = 120](https://img.qammunity.org/2019/formulas/mathematics/high-school/to0mn05u51djizuyfxg591ncd2ihq9iahd.png)
And finally divide both sides by 3.
![y = (120)/(3) = 40](https://img.qammunity.org/2019/formulas/mathematics/high-school/h08j6pbjjhpij5wefg8xp44y4690d32p6t.png)
Hence, the answer is B.
~ Hope this helps you!