In this question, angle 5 and angle 2 are linear pair. And angles of linear pair are supplementary angles .
Therefore
![\angle 5 + \angle 2=180](https://img.qammunity.org/2019/formulas/mathematics/middle-school/15v1gvxh1smdi7mktn6lyeo5fq3k7mofi5.png)
And sum of interior angles of a triangle is 180 degree, that is
![\angle 1 + \angle 2 + \angle 3 =180](https://img.qammunity.org/2019/formulas/mathematics/middle-school/nslatzgroq591wkgrvoa66gdemn2aocok4.png)
SInce both the equations have 180 in the right side, left side of both equations are equal too . That is
![\angle 5 + \angle 2 = \angle 1 + \angle 2 + \angle 3](https://img.qammunity.org/2019/formulas/mathematics/middle-school/nv3aekpk5jya9ogx3uv1kkyrwll8jvibe5.png)
Which gives
![\angle 5=\angle 1 + \angle 3](https://img.qammunity.org/2019/formulas/mathematics/middle-school/d2of1dfvi5exvq7e8atthr1p23pfagrt86.png)
So the correct option is A .