$\"\"$

Let n be the number.

Sum of a number and 9 is $\"\"$ .

The equation is $\"\"$ .

Apply subtraction property of equality: Subtract 9 from each side.

$\"\"$

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

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

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

Check:

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

$\"\"$

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

The statement is true. $\"\"$

The value of $\"\"$ .