5. If AABC = ADEF, find the measure of

Can someone explain me?

Option A) angle B = 67°

Step-by-step explanation:

I'll use " [ " symbol for saying angle.

Alright so ...

since triangle ABC and triangle DEF are congruent

it means [ A = [ D

[ B = [ E

[ C = [ F

here [ A = 78° (which means [ D is also 78°)

and ..[ F = 35° (which means [ C is also 35°)

-->So now all you need to know to find [ B is to know the other two angles in the triangle. and thats where ..

you write.. [ A + [ B + [ C = 180° (angle sum property)

78° + [ B + 35° = 180°

113° + [ B = 180°

[ B = 180 - 113

= 67°

I hope that clears the concept , if you have any questions regarding it I'd love to help .