| ( | 200 | + | 10 | y | ) | ( | 64 | − | y | ) | = | 14400 |
| 方程左边 = | 200 | ( | 64 | − | y | ) | + | 10 | y | ( | 64 | − | y | ) |
| = | 200 | × | 64 | − | 200 | y | + | 10 | y | ( | 64 | − | y | ) |
| = | 12800 | − | 200 | y | + | 10 | y | ( | 64 | − | y | ) |
| = | 12800 | − | 200 | y | + | 10 | y | × | 64 | − | 10 | y | y |
| = | 12800 | − | 200 | y | + | 640 | y | − | 10 | y | y |
| = | 12800 | + | 440 | y | − | 10 | y | y |
| 12800 | + | 440 | y | − | 10 | y | y | = | 14400 |