Answer:
[tex]x=19[/tex]
Step-by-step explanation:
The perimeter of a shape is the sum of all of its side lengths. Therefore, the perimeter of the first triangle is [tex]x-7+x-7+x-7=3x-21[/tex] and the perimeter of the second triangle is [tex]9+15+12=36[/tex].
We are given that the perimeters of the triangles are equal, so [tex]3x-21[/tex] equals [tex]36[/tex]. As an equation, that would be [tex]3x-21=36[/tex]. Solving for [tex]x[/tex], we get:
[tex]3x-21=36[/tex]
[tex]3x=57[/tex] (Add [tex]21[/tex] to both sides of the equation to isolate [tex]x[/tex])
[tex]x=19[/tex] (Divide both sides of the equation by [tex]3[/tex] to get rid of [tex]x[/tex]'s coefficient)
Hope this helps!
