Question

if triangle abc cogruent to def a=50 f=60 then find b

Answer 1

In ∆ ABC
Angle A = 50°
Angle C = Angle F = 60° { Since both ∆'s are congruent}

Now,
A+B+C = 180° { Angle sum property}
50 + B + 60 = 180°
110° + B = 180°
B = 180-110
Angle B = 70°

Hope it helps.