Answer
$x = 6$
Work Step by Step
We use distributive property to expand the equation:
$9x + 63 - (6x - 18) = 99\\
9x+63-6x-(-18)=99\\
9x+63-6x+18=99$
Combine like terms:
$(9x - 6x) + (63 + 18) = 99$
$3x + 81 = 99$
Subtract $81$ from each side of the equation to isolate constants to the right side of the equation:
$3x = 18$
Divide each side by $3$ to solve for $x$:
$x = 6$
