In the following figure, if $\angle 1+\angle 3=120°$ , then $\angle 2+\angle 4$ is equal to

$\angle 1+\angle 3=120°$       ($\because \angle 1=\angle 3$   vertically opposite angles are equal)

$2\angle 3=120°\Rightarrow \angle 3=60°$

$\angle 3+\angle 4=180°\Rightarrow \angle 4=180°-60°=120°$

$\angle 2+\angle 4=120°+120°=240°$ ($\because \angle 2=\angle 4$   vertically opposite angles are equal)