Step-by-step explanation:
So you must know the sum of interior angles of a triangle is 180 degrees. then denote each angle a,b and c. so you will get something like this
a+b+c =180
and if a=25 and the rest angles are congruent, then u can
b=c, then substitute and you will get it:-
a+b+c = 180
25+b+b =180 (substituted c by b since they are equal)
25+2b =180
2b = 180 - 25 (collecting like terms)
2b = 155
b = 77.5 (Dividing by 2)
Hope I helped :)