Consider the diagram below of an equilatera triangle.

Answer:
4 = n.
13 ft.
Step-by-step explanation:
An equilateral triangle means that all of the sides are equal.
This means: 2n + 5 = 3n + 1 = 5n -7
You can pick two of those sides to set up an equation to solve for n.
For example, 2n + 5 = 3n + 1.
Then you will need to isolate the variable.
Subtract 1 from each side to get 2n + 4 = 3n.
Subtract 2n from each side to get 4 = n.
Substitue 4 for n into one of the equations.
2n + 5
2(4) + 5
8 + 5 = 13
Each side is 13 ft.