For an equilateral triangle , all the sides are equal. Therefore, the perimeter of the equilateral triangle above is the sum of all it sides.
The sum is calculated below
[tex]\begin{gathered} \text{perimeter = 1.5x+5+1.5x+5}+\text{1.5x+5} \\ \text{perimeter}=4.5x+15 \end{gathered}[/tex]
The answer is C.
