The angles of a quadrilateral are x, 5x+15°, 3x-25°, and 4x-20°. Find the measure of the largest angle of the quadrilateral.
The sum of the measures of the interior angles of a quadrilateral = 360°........so we have
x + [5x + 15] + [3x - 25] + [ 4x - 20] = 360 simplify
13x - 30 = 360 add 30 to both sides
13x = 390 divide both sides by 13
x = 30
The largest angle is 5x + 15 = 165°