In an a-frame house, the two congruent sides each form a 76° angle with the ground. what is the angle formed at the peak by the two sides?

This triangle-like A having at it base 2 congruent angle is an isosceles Triangle:
The sum of all angles in a triangle = 180°, 

45° + 45° + Peak angle = 180°

Peak angle° = 180° - 90° = 90°

2+1=3 that’s your answer