| ( | 10 | − | y | ) | ( | 200 | + | 50 | y | ) | = | 2450 |
| Left side of the equation = | 10 | ( | 200 | + | 50 | y | ) | − | y | ( | 200 | + | 50 | y | ) |
| = | 10 | × | 200 | + | 10 | × | 50 | y | − | y | ( | 200 | + | 50 | y | ) |
| = | 2000 | + | 500 | y | − | y | ( | 200 | + | 50 | y | ) |
| = | 2000 | + | 500 | y | − | y | × | 200 | − | y | × | 50 | y |
| = | 2000 | + | 300 | y | − | y | × | 50 | y |
| 2000 | + | 300 | y | − | y | × | 50 | y | = | 2450 |