Question

2 angles of quadrilateral are ${70}^o$ and ${80}^o$ third angle is supplementary of ${70}^o$ find the $4^{th}$ angle.

Answer 1

Angles $={70}^o,{80}^o$

$3^{rd}$ Angle $=180-{70}^o=110$

$4^{th}$ angle $=x$

$\Rightarrow 70+80+110+x={360}^o$

$x={360}^o-{260}^o$

$x={100}^o$.