$\"\"$ $\"\"$

The equation is $\"\"$ .

$\"\"$ (Product of two same signs is positive)

According to subtraction property of equality: Subtract 18 from each side.

$\"\"$

$\"\"$ (Apply commutative property of addition: $\"\"$ )

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

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

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

Check:

To check the solution, substitute $\"\"$ in original equation.

$\"\"$

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

Compare the values, the equation is true. The solution is $\"\"$ . $\"\"$

The value of $\"\"$ .