| ( | 35 | + | 2 5 | × | x% | ) | ( | 20 | + | x% | ) | = | 1600 |
| 方程左边 = | 35 | ( | 20 | + | x% | ) | + | 2 5 | × | x% | ( | 20 | + | x% | ) |
| = | 35 | ( | 20 | + | x% | ) | + | 1 250 | x | ( | 20 | + | x% | ) |
| = | 35 | × | 20 | + | 35 | × | x% | + | 1 250 | x | ( | 20 | + | x% | ) |
| = | 700 | + | 7 20 | x | + | 1 250 | x | ( | 20 | + | x% | ) |
| = | 700 | + | 7 20 | x | + | 1 250 | x | × | 20 | + | 1 250 | x | × | x% |
| = | 700 | + | 7 20 | x | + | 2 25 | x | + | 1 25000 | x | x |
| = | 700 | + | 43 100 | x | + | 1 25000 | x | x |
| 700 | + | 43 100 | x | + | 1 25000 | x | x | = | 1600 |