$\"\"$

The expression is $\"\"$ .

$\"\"$ (Write the equation)

$\"\"$ (Subtract 18 from each side)

$\"\"$ (Subtract: $\"\"$ )

$\"\"$ (Apply additive identity property: $\"\"$ )

$\"\"$ (Multiply negative one to each side)

$\"\"$ (Multiply: $\"\"$ )

The solution is $\"\"$ . $\"\"$

Check:

Substitute $\"\"$ in the equation.

$\"\"$ (Write the equation)

$\"\"$ (Substitute $\"\"$ )

$\"\"$ (Multiply: $\"\"$ )

$\"\"$ (Add: $\"\"$ )

The solution was checked. $\"\"$

The solution is $\"\"$ .