| ( | 200 | − | y | ) | ( | 20 | + | 2 | y | ) | = | 1150 |
| Left side of the equation = | 200 | ( | 20 | + | 2 | y | ) | − | y | ( | 20 | + | 2 | y | ) |
| = | 200 | × | 20 | + | 200 | × | 2 | y | − | y | ( | 20 | + | 2 | y | ) |
| = | 4000 | + | 400 | y | − | y | ( | 20 | + | 2 | y | ) |
| = | 4000 | + | 400 | y | − | y | × | 20 | − | y | × | 2 | y |
| = | 4000 | + | 380 | y | − | y | × | 2 | y |
| 4000 | + | 380 | y | − | y | × | 2 | y | = | 1150 |