Respuesta :

Step-by-step explanation:

The two terms that are alike are 14x and x.

Add both of the terms;

[tex]15x+3x^3-9[/tex]

Format the trinomial, exponents first, then variable(s);

[tex]\boxed{The \: correct \: option \:is \:C. \:3x^3+15x-9}[/tex]