| 10 | x | + | 8 | + | 10 | × | 100 | + | ( | 200 | − | x | − | 100 | ) | × | 10 | × | 9 10 | = | 1988 |
| 方程左边 = | 10 | x | + | 8 | + | 1000 | + | ( | 200 | − | x | − | 100 | ) | × | 9 |
| = | 10 | x | + | 1008 | + | ( | 200 | − | x | − | 100 | ) | × | 9 |
| 10 | x | + | 1008 | + | ( | 200 | − | x | − | 100 | ) | × | 9 | = | 1988 |
| 方程左边 = | 10 | x | + | 1008 | + | 200 | × | 9 | − | x | × | 9 | − | 100 | × | 9 |
| = | 10 | x | + | 1008 | + | 1800 | − | x | × | 9 | − | 900 |
| = | 1 | x | + | 1908 |
| 1 | x | + | 1908 | = | 1988 |
| 1 | x | = | 1988 | − | 1908 |
| x | = | 1988 | − | 1908 |
| x | = | 80 |