This triangle has 60 degrees already. Remember that the sum of all triangles have to be 180.
Since we have two y's we can simplify it as 2y + 60 = 180.
We can now set this up as an algebraic equation.
2y + 60 = 180
Subtract 60 from both sides.
2y = 120
Divide both sides by 2
y = 60.
Y = 60, your answer is D.)
I hope this helps!