| ( | 70 | ( | 1 | + | 20 100 | ) | ) | + | ( | 7 100 | x | ) | = | x |
| 方程左边 = | 70 | ( | 1 | + | 20 100 | ) | + | ( | 7 100 | x | ) |
| = | 70 | × | 1 | + | 70 | × | 20 100 | + | ( | 7 100 | x | ) |
| = | 70 | + | 14 | + | ( | 7 100 | x | ) |
| = | 84 | + | ( | 7 100 | x | ) |
| = | 84 | + | 7 100 | x |
| 84 | + | 7 100 | x | = | x |
7 100 | x | − | x | = | - | 84 |
| - | 93 100 | x | = | - | 84 |
| 84 | = | 93 100 | x |
93 100 | x | = | 84 |
| x | = | 84 | ÷ | 93 100 |
| = | 84 | × | 100 93 |
| = | 28 | × | 100 31 |
| x | = | 2800 31 |
| x | = | 90.322581 |