| 3 | ÷ | 4 | × | x | + | ( | 400 | − | x | ) | × | 4 | ÷ | 9 | = | 245 |
| 方程左边 = | 3 4 | x | + | ( | 400 | − | x | ) | × | 4 9 |
3 4 | x | + | ( | 400 | − | x | ) | × | 4 9 | = | 245 |
| 方程左边 = | 3 4 | x | + | 400 | × | 4 9 | − | x | × | 4 9 |
| = | 3 4 | x | + | 1600 9 | − | x | × | 4 9 |
| = | 11 36 | x | + | 1600 9 |
11 36 | x | + | 1600 9 | = | 245 |
11 36 | x | = | 245 | − | 1600 9 |
11 36 | x | = | 605 9 |
| x | = | 605 9 | ÷ | 11 36 |
| = | 605 9 | × | 36 11 |
| = | 55 | × | 4 |
| x | = | 220 |