| ( | 200 | + | y | ) | ( | 64 | − | 10 | y | ) | = | 14400 |
| Left side of the equation = | 200 | ( | 64 | − | 10 | y | ) | + | y | ( | 64 | − | 10 | y | ) |
| = | 200 | × | 64 | − | 200 | × | 10 | y | + | y | ( | 64 | − | 10 | y | ) |
| = | 12800 | − | 2000 | y | + | y | ( | 64 | − | 10 | y | ) |
| = | 12800 | − | 2000 | y | + | y | × | 64 | − | y | × | 10 | y |
| = | 12800 | − | 1936 | y | − | y | × | 10 | y |
| 12800 | − | 1936 | y | − | y | × | 10 | y | = | 14400 |