If triangle ABC is congruent to triangle DEF, their interior angles are congruent, because congruent parts of congruent triangles are congruent (CPCTC).
That means ∠D is congruent to ∠A; ∠D is equal to 8x - 2.
Interior angles of all triangles add to equal 180 degrees, so you can set the sum of these interior angle values equal to 180 and solve for x.
180 = (8x - 2) + 22 + 72
180 = 8x - 2 + 22 + 72
180 = 8x + 92
88 = 8x
11 = x
Answer:
x = 11
