| ( | 1000 | + | 1500 | ) | x | + | ( | 300 | + | 100 | ) | x | × | 3 | = | 42000 |
| 方程左边 = | 1000 | x | + | 1500 | x | + | ( | 300 | + | 100 | ) | x | × | 3 |
| = | 2500 | x | + | ( | 300 | + | 100 | ) | x | × | 3 |
| = | 2500 | x | + | 300 | x | × | 3 | + | 100 | x | × | 3 |
| = | 2500 | x | + | 900 | x | + | 300 | x |
| = | 3700 | x |
| 3700 | x | = | 42000 |
| x | = | 42000 | ÷ | 3700 |
| = | 42000 | × | 1 3700 |
| = | 420 | × | 1 37 |
| x | = | 420 37 |
| x | = | 11.351351 |