An isosceles trapezoind is a traipezoid with the two base angles equal and the two up angles equal.
Sum of interior angles of a quadrilateral = 360 degrees
i.e. angle WXY + angle XYZ + angle YZW + angle ZWX = 360 degrees
But angle WXY = angle ZWX and angle XYZ = angle YZW
Therefore, 2(6x + 10) + 2(5x + 5) = 360
12x + 20 + 10x + 10 = 360
22x = 360 - 30 = 330
x = 330 / 22 = 15
Therefore, angle YZW = 5(15) + 5 = 75 + 5 = 80 degrees.