Elementary Algebra

$= -13$
1. We substitute the $x, y, and \space z$ values into the equation using parenthesis: $x + y - z$ for $x = -18$, $y = 13$, $z = 8$ $= (-18) + (13) - 8$ $= - 18 + 13 - 8$ $= -26 + 13$ $= -13$