| ( | 10 | a | + | 1 | ) | ÷ | ( | a | + | 1 | ) | × | 3 10 | + | ( | 10 | a | + | 8 | ) | ÷ | ( | a | + | 1 | ) | × | 7 10 | = | 199 20 |
| 方程两边同时乘以: | ( | a | + | 1 | ) |
| ( | 10 | a | + | 1 | ) | × | 3 10 | + | ( | 10 | a | + | 8 | ) | × | 7 10 | = | 199 20 | ( | a | + | 1 | ) |
| 10 | a | × | 3 10 | + | 1 | × | 3 10 | + | ( | 10 | a | + | 8 | ) | × | 7 10 | = | 199 20 | ( | a | + | 1 | ) |
| 10 | a | × | 3 10 | + | 1 | × | 3 10 | + | ( | 10 | a | + | 8 | ) | × | 7 10 | = | 199 20 | a | + | 199 20 | × | 1 |
| 3 | a | + | 3 10 | + | ( | 10 | a | + | 8 | ) | × | 7 10 | = | 199 20 | a | + | 199 20 |
| 3 | a | + | 3 10 | + | 10 | a | × | 7 10 | + | 8 | × | 7 10 | = | 199 20 | a | + | 199 20 |
| 3 | a | + | 3 10 | + | 7 | a | + | 28 5 | = | 199 20 | a | + | 199 20 |
| 10 | a | + | 59 10 | = | 199 20 | a | + | 199 20 |
| 10 | a | − | 199 20 | a | = | 199 20 | − | 59 10 |
1 20 | a | = | 199 20 | − | 59 10 |
1 20 | a | = | 81 20 |
| a | = | 81 20 | ÷ | 1 20 |
| = | 81 20 | × | 20 |
| = | 81 | × | 1 |
| a | = | 81 |