## Elementary Algebra

$= 9$
1. We first substitute the $x, y, and \space z$ values into the equation using parenthesis: $-x + y + z$ for $x = -11$, $y = 7$, $z = -9$ $= -(-11)+7 + (-9)$ 2. A double negative such as "$-(-11)$" will cancel out to become "$11$", a positive number while a positive and a negative number like "$+(-9)$" will become "$-9$", a negative number : $= 11 + 7 - 9$ $= 18 - 9$ $= 9$