Question

Also this question tooo pleease, PS: what topic is this
Solve for x.

Answer 1

This falls under geometry. The two labeled angles are congruent, which means the line segment between them (AD in the image) is a bisector of the angle at vertex A. Use the angle bisector theorem, which says that

`(BD)/(DC)=(AB)/(AC)\iff(12)/((5+9x)-12)=(15)/(25)`

`(12)/(9x-7)=\frac35`

`20=9x-7`

`x=3`