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

The expression is $\"\"$ .

According to addition property of equality: Add 7 to each side.

$\"\"$

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

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

Check:

Check the solution by substituting $\"\"$ in the original equation.

$\"\"$

$\"\"$ (Subtract: 13 – 7 = 6) $\"\"$

The value of $\"\"$ .