| ( | y | − | 50 | ) | × | 5 | ( | 100 | − | y | ) | = | 4000 |
| Left side of the equation = | y | × | 5 | ( | 100 | − | y | ) | − | 50 | × | 5 | ( | 100 | − | y | ) |
| = | y | × | 5 | ( | 100 | − | y | ) | − | 250 | ( | 100 | − | y | ) |
| = | y | × | 5 | × | 100 | − | y | × | 5 | y | − | 250 | ( | 100 | − | y | ) |
| = | y | × | 500 | − | y | × | 5 | y | − | 250 | ( | 100 | − | y | ) |
| = | 500 | y | − | y | × | 5 | y | − | 250 | × | 100 | + | 250 | y |
| = | 500 | y | − | y | × | 5 | y | − | 25000 | + | 250 | y |
| = | 750 | y | − | y | × | 5 | y | − | 25000 |
| 750 | y | − | y | × | 5 | y | − | 25000 | = | 4000 |