| 16000 | + | 10 | y | ( | 80 | − | y | ) | − | 50 | ( | 200 | + | 10 | ( | 80 | − | y | ) | ) | = | 9000 |
| Left side of the equation = | 16000 | + | 10 | y | × | 80 | − | 10 | y | y | − | 50 | ( | 200 | + | 10 | ( | 80 | − | y | ) | ) |
| = | 16000 | + | 800 | y | − | 10 | y | y | − | 50 | ( | 200 | + | 10 | ( | 80 | − | y | ) | ) |
| = | 16000 | + | 800 | y | − | 10 | y | y | − | 50 | × | 200 | − | 50 | × | 10 | ( | 80 | − | y | ) |
| = | 16000 | + | 800 | y | − | 10 | y | y | − | 10000 | − | 500 | ( | 80 | − | y | ) |
| = | 6000 | + | 800 | y | − | 10 | y | y | − | 500 | ( | 80 | − | y | ) |
| = | 6000 | + | 800 | y | − | 10 | y | y | − | 500 | × | 80 | + | 500 | y |
| = | 6000 | + | 800 | y | − | 10 | y | y | − | 40000 | + | 500 | y |
| = | - | 34000 | + | 1300 | y | − | 10 | y | y |
| - | 34000 | + | 1300 | y | − | 10 | y | y | = | 9000 |