In this case it is x^5 x^5(x^3+3) when you multiply with variables that have exponents the exponents are added therefore if you have x^5 and the problem states x^8 you would have x^3 left over in parentheses With the 3x^% you would have a 3 so the problem x^8+3x^5=x^5(x^3+3)
