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

The equation is $\"\"$ .

According to addition property of equality: Add 2.78 to each side.

$\"\"$

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

$\"\"$ (Apply Aadditive identity 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 $\"\"$ .