| ( | 12 | − | 2 | y | ) | ( | 28 | − | 2 | y | ) | ÷ | 2 | = | 130 |
| Left side of the equation = | 12 | ( | 28 | − | 2 | y | ) | × | 1 2 | − | 2 | y | ( | 28 | − | 2 | y | ) | × | 1 2 |
| = | 6 | ( | 28 | − | 2 | y | ) | − | 1 | y | ( | 28 | − | 2 | y | ) |
| = | 6 | × | 28 | − | 6 | × | 2 | y | − | 1 | y | ( | 28 | − | 2 | y | ) |
| = | 168 | − | 12 | y | − | 1 | y | ( | 28 | − | 2 | y | ) |
| = | 168 | − | 12 | y | − | 1 | y | × | 28 | + | 1 | y | × | 2 | y |
| = | 168 | − | 12 | y | − | 28 | y | + | 2 | y | y |
| = | 168 | − | 40 | y | + | 2 | y | y |
| 168 | − | 40 | y | + | 2 | y | y | = | 130 |