| ( | 68 | − | 2 | y | − | 40 | ) | ( | 600 | − | 140 | + | 4 | y | ) | + | 3920 | = | 6800 |
| Left side of the equation = | 68 | ( | 600 | − | 140 | + | 4 | y | ) | − | 2 | y | ( | 600 | − | 140 | + | 4 | y | ) | − | 40 | ( | 600 | − | 140 | + | 4 | y | ) | + | 3920 |
| = | 68 | × | 600 | − | 68 | × | 140 | + | 68 | × | 4 | y | − | 2 | y | ( | 600 | − | 140 | + | 4 | y | ) | − | 40 | ( | 600 | − | 140 | + | 4 | y | ) |
| = | 40800 | − | 9520 | + | 272 | y | − | 2 | y | ( | 600 | − | 140 | + | 4 | y | ) | − | 40 | ( | 600 | − | 140 | + | 4 | y | ) | + | 3920 |
| = | 35200 | + | 272 | y | − | 2 | y | ( | 600 | − | 140 | + | 4 | y | ) | − | 40 | ( | 600 | − | 140 | + | 4 | y | ) |
| = | 35200 | + | 272 | y | − | 2 | y | × | 600 | + | 2 | y | × | 140 | − | 2 | y | × | 4 |
| = | 35200 | + | 272 | y | − | 1200 | y | + | 280 | y | − | 8 | y | y | − | 40 | ( | 600 | − | 140 | + | 4 | y | ) |
| = | 35200 | − | 648 | y | − | 8 | y | y | − | 40 | ( | 600 | − | 140 | + | 4 | y | ) |
| = | 35200 | − | 648 | y | − | 8 | y | y | − | 40 | × | 600 | + | 40 | × | 140 | − | 40 | × | 4 |
| = | 35200 | − | 648 | y | − | 8 | y | y | − | 24000 | + | 5600 | − | 160 | y |
| = | 16800 | − | 808 | y | − | 8 | y | y |
| 16800 | − | 808 | y | − | 8 | y | y | = | 6800 |