The given triangle has two sides marked equal and hence is an isosceles triangle.In isosceles triangle base angles are equal <A=<B=50.
Sum of angles in any triangle is 180 degrees.
<A+<B+<C=180°
50+50+5y+10=180
Adding like terms :
110+5y=180
Subtracting 110 on both sides:
5y=70
Dividing both sides by 5:
y=14.
