We know that the triangles ABC and DEF are congruent to each other. Therefore each of the sides and angles of triangle ABC correspond to the sides and angles of triangle DEF.
It means that A corresponds to D, B corresponds to E and C corresponds to F.
We are given the value for the angle A which is equal to 65° and corresponds to angle D, with a value of (x - 8)°, of the other triangle, so we can write:
