$\"\"$

The equation is $\"\"$ .

Addition property of equality: if a = b, then a $\"\"$ c = b $\"\"$ c.

$\"\"$ (Add 2.78 to each side)

$\"\"$ (Additive inverse property: $\"\"$ )

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

$\"\"$

Check:

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

$\"\"$

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

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

$\"\"$

The value of $\"\"$ .