| 1 | + | x% | = | 9 10 | ( | 1 | + | ( | x | + | 15 | ) | × | 1 100 | ) |
| 方程右边 = | 9 10 | × | 1 | + | 9 10 | ( | x | + | 15 | ) | × | 1 100 |
| = | 9 10 | + | 9 1000 | ( | x | + | 15 | ) |
| = | 9 10 | + | 9 1000 | x | + | 9 1000 | × | 15 |
| = | 9 10 | + | 9 1000 | x | + | 27 200 |
| = | 207 200 | + | 9 1000 | x |
| 1 | + | x% | = | 207 200 | + | 9 1000 | x |
| x% | − | 9 1000 | x | = | 207 200 | − | 1 |
1 1000 | x | = | 207 200 | − | 1 |
1 1000 | x | = | 7 200 |
| x | = | 7 200 | ÷ | 1 1000 |
| = | 7 200 | × | 1000 |
| = | 7 | × | 5 |
| x | = | 35 |