| ( | y | − | 6 | ) | ( | 300 | + | 3 | y | ) | = | 6300 |
| Left side of the equation = | y | ( | 300 | + | 3 | y | ) | − | 6 | ( | 300 | + | 3 | y | ) |
| = | y | × | 300 | + | y | × | 3 | y | − | 6 | ( | 300 | + | 3 | y | ) |
| = | 300 | y | + | y | × | 3 | y | − | 6 | × | 300 | − | 6 | × | 3 | y |
| = | 300 | y | + | y | × | 3 | y | − | 1800 | − | 18 | y |
| = | 282 | y | + | y | × | 3 | y | − | 1800 |
| 282 | y | + | y | × | 3 | y | − | 1800 | = | 6300 |