Like terms are terms that contain the same variables, and raised to the same power. The numerical coefficients can be different, but the variables AND the exponents must be the same.
In the equation given, 2 and 5 are the coefficients. "x" is the variable, and 5 and 3 are the exponents. Even though the variables are the same, the exponents are not! This means, that each term is separate, and are not like. You cannot combine 2x^5 and 3x^3.
