Which phrase describes the algebraic expression x minus 21.5? 21.5 decreased by x
x more than 21.5
21.5 minus x
x less 21.5

Pemdas = Parenthesis, exponents, multiply, divide, addition, subtract. So first you need to break it down and solve all in parenthesis by distributing the 3, so 3*x^2 = 3x^2 & 3*-7= -21. NEW equation would be 19x^2+7-[3x^2-21+9]. Now you're going to distribute that negative sign and combine like terms. 19x^2 -3x^2 is now 16x^2. 7-(-21)+9 solve for that which is 7+21 = 28 then add the 9 which will now be 37. so the simplify answer is now 16x^2 + 28