Remember PEMDAS: Parentheses, exponents, multipulcation, division, addition, and subtraction. [(15(10)-12(10]/10. Parentheses first. you should do the things inside the brackets first. so it'd go like, [150-120]/10 then you subtract whats in the parenthese, so it will turn out as 30/10, then simply divide, and it turns out to be 3.