\\(\\begin{array}{l}{\ ext { It can be observed that, }} \\\\ {x+y+z+w=360^{\\circ}(\ ext { Complete angle })} \\\\ {\ ext { It is given that, }} \\\\ {x+y=z+w} \\\\ {\ herefore x+y+x+y=360^{\\circ}} \\\\ {2(x+y)=360^{\\circ}} \\\\ {x+y=180^{\\circ}}\\end{array}\\)
Since x and y form a linear pair, AOB is a line.