The two little lines through the two sides of the triangle mean that they are the same length.
When two sides of a triangle are the same, the two lower inside angles are also the same.
Angle A is given as 50 degrees, so angle C is also 50 degrees.
The sum of the three inside angles need to equal 180 degrees, so angle B would equal 180 - 50 - 50 = 80 degrees.
Angle B = 80
Angle C = 50
