Question

Find the value of "Y"

​

Answer 1

∠ABC=2×∠ADC

so,∠ABC=2×85= 170°

we know that some of all angle in quadrilateral =360°

∠A+∠B+∠C+∠D=360°

85°+170°+2∠A=360°( Because ∠A=∠C)

2∠A=360°-255°

∠A=115/2=57.5°

so y=180°-57.5°=122.5°