Ok, using PEMDAS we need to distribute the parentheses first. To do that we do -3x times x plus -3x times 4. This gets us to 6x-3x^2-12x. To simplify even mroe we need to combine like terms, which is x. So, 6x-12x can be combined into -6x. Since -3x^2 has no like terms, we have then finished simplifying the equation, which is: -6x-3x^2
*disclaimer: i am sorry if i got this wrong lol. You may want to double check
