| ( | 200 | + | x | ) | ( | 20 | + | x | ÷ | 20 | ) | = | 11520 |
| 方程左边 = | 200 | ( | 20 | + | x | ÷ | 20 | ) | + | x | ( | 20 | + | x | ÷ | 20 | ) |
| = | 200 | × | 20 | + | 200 | x | ÷ | 20 | + | x | ( | 20 | + | x | ÷ | 20 | ) |
| = | 4000 | + | 10 | x | + | x | ( | 20 | + | x | ÷ | 20 | ) |
| = | 4000 | + | 10 | x | + | x | × | 20 | + | x | x | ÷ | 20 |
| = | 4000 | + | 30 | x | + | x | x | × | 1 20 |
| 4000 | + | 30 | x | + | x | x | × | 1 20 | = | 11520 |