angle A:
opposite angles are equal-> a= 35°
angle B:
angles in a triangle are ALWAYS equal to 180°->
b= 180°-a- a right angle
b= 180°-35°-90°
b= 55°
angle C:
angle c and the angle next to it (70°) are supplementary, meaning that added up they are 180°. You can see it on the drawing bc they form a straight line.
C= 180°-70°
C= 110°