| ( | 100 | − | y | ) | ( | 300 | + | 5 | y | ) | = | 32000 |
| Left side of the equation = | 100 | ( | 300 | + | 5 | y | ) | − | y | ( | 300 | + | 5 | y | ) |
| = | 100 | × | 300 | + | 100 | × | 5 | y | − | y | ( | 300 | + | 5 | y | ) |
| = | 30000 | + | 500 | y | − | y | ( | 300 | + | 5 | y | ) |
| = | 30000 | + | 500 | y | − | y | × | 300 | − | y | × | 5 | y |
| = | 30000 | + | 200 | y | − | y | × | 5 | y |
| 30000 | + | 200 | y | − | y | × | 5 | y | = | 32000 |