| ( | ( | 70 | − | x | ) | × | 1 5 | + | 40 | + | ( | 50 | + | x | ) | × | 4 5 | ) | ÷ | 200 | = | 47 100 | + | 3 20 |
| 方程左边 = | ( | 70 | − | x | ) | × | 1 5 | × | 1 200 | + | 40 | × | 1 200 | + | ( | 50 | + | x | ) | × | 4 5 | × | 1 200 |
| = | ( | 70 | − | x | ) | × | 1 1000 | + | 1 5 | + | ( | 50 | + | x | ) | × | 1 250 |
| = | 70 | × | 1 1000 | − | x | × | 1 1000 | + | 1 5 | + | ( | 50 | + | x | ) | × | 1 250 |
| = | 7 100 | − | x | × | 1 1000 | + | 1 5 | + | ( | 50 | + | x | ) | × | 1 250 |
| = | 27 100 | − | 1 1000 | x | + | ( | 50 | + | x | ) | × | 1 250 |
| = | 27 100 | − | 1 1000 | x | + | 50 | × | 1 250 | + | x | × | 1 250 |
| = | 27 100 | − | 1 1000 | x | + | 1 5 | + | x | × | 1 250 |
| = | 47 100 | + | 3 1000 | x |
47 100 | + | 3 1000 | x | = | 47 100 | + | 3 20 |
| 方程右边 = | 31 50 |
47 100 | + | 3 1000 | x | = | 31 50 |
3 1000 | x | = | 31 50 | − | 47 100 |
3 1000 | x | = | 3 20 |
| x | = | 3 20 | ÷ | 3 1000 |
| = | 3 20 | × | 1000 3 |
| = | 1 | × | 50 |
| x | = | 50 |