Question

please answer this question

Answer 1

let ABCD is a quadrilateral .
angle ABC = BCD = X
ABC + BCD = 180 (CO.INTERIOR ANGLE.)
x + x = 180
x= 90=ABC = BCD
ACD + BCD = 180 ( co Interior angle)
so angle ACD = 180- BCD = 90.
so , the qua. ABCD IS A square.
Hence AD // BC.