| ( | 4 | y | + | 8 | ) | ( | 2900 | − | 50 | y | − | 2500 | ) | = | 5000 |
| Left side of the equation = | 4 | y | ( | 2900 | − | 50 | y | − | 2500 | ) | + | 8 | ( | 2900 | − | 50 | y | − | 2500 | ) |
| = | 4 | y | × | 2900 | − | 4 | y | × | 50 | y | − | 4 | y | × | 2500 | + | 8 | ( | 2900 | − | 50 | y | − | 2500 | ) |
| = | 11600 | y | − | 200 | y | y | − | 10000 | y | + | 8 | ( | 2900 | − | 50 | y | − | 2500 | ) |
| = | 1600 | y | − | 200 | y | y | + | 8 | ( | 2900 | − | 50 | y | − | 2500 | ) |
| = | 1600 | y | − | 200 | y | y | + | 8 | × | 2900 | − | 8 | × | 50 | y | − | 8 | × | 2500 |
| = | 1600 | y | − | 200 | y | y | + | 23200 | − | 400 | y | − | 20000 |
| = | 1200 | y | − | 200 | y | y | + | 3200 |
| 1200 | y | − | 200 | y | y | + | 3200 | = | 5000 |