For the diagram below let m∠1 = (7x + 5)°, m∠2 = (9x − 8)°, and m∠3 = (11x − 15)°. A triangle with exterior angles 1, 2, 3. Complete the work shown to find the m∠3. Set the sum of the exterior angles to 360° and solve for x. 7x + 5 + 9x − 8 + 11x − 15 = 360 27x − 18 = 360 27x = 378 x = 14 Substitute the value of x into the expression that represents mAngle3. mAngle3 = 11(14) – 15 mAngle3 = °