| ( | 26 | − | y | ) | ( | 240 | + | 20 | y | ) | = | 6500 |
| Left side of the equation = | 26 | ( | 240 | + | 20 | y | ) | − | y | ( | 240 | + | 20 | y | ) |
| = | 26 | × | 240 | + | 26 | × | 20 | y | − | y | ( | 240 | + | 20 | y | ) |
| = | 6240 | + | 520 | y | − | y | ( | 240 | + | 20 | y | ) |
| = | 6240 | + | 520 | y | − | y | × | 240 | − | y | × | 20 | y |
| = | 6240 | + | 280 | y | − | y | × | 20 | y |
| 6240 | + | 280 | y | − | y | × | 20 | y | = | 6500 |