| ( | 220 | − | 200 | ) | ÷ | ( | 500 | − | 220 | ) | = | ( | A | − | 9 | ) | ÷ | ( | 209 10 | − | A | ) |
| 方程两边同时乘以: | ( | 500 | − | 220 | ) | , | ( | 209 10 | − | A | ) |
| ( | 220 | − | 200 | ) | ( | 209 10 | − | A | ) | = | ( | A | − | 9 | ) | ( | 500 | − | 220 | ) |
| 220 | ( | 209 10 | − | A | ) | − | 200 | ( | 209 10 | − | A | ) | = | ( | A | − | 9 | ) | ( | 500 | − | 220 | ) |
| 220 | ( | 209 10 | − | A | ) | − | 200 | ( | 209 10 | − | A | ) | = | A | ( | 500 | − | 220 | ) | − | 9 | ( | 500 | − | 220 | ) |
| 220 | × | 209 10 | − | 220 | A | − | 200 | ( | 209 10 | − | A | ) | = | A | ( | 500 | − | 220 | ) | − | 9 | ( | 500 | − | 220 | ) |
| 220 | × | 209 10 | − | 220 | A | − | 200 | ( | 209 10 | − | A | ) | = | A | × | 500 | − | A | × | 220 | − | 9 | ( | 500 | − | 220 | ) |
| 4598 | − | 220 | A | − | 200 | ( | 209 10 | − | A | ) | = | A | × | 500 | − | A | × | 220 | − | 9 | ( | 500 | − | 220 | ) |
| 4598 | − | 220 | A | − | 200 | ( | 209 10 | − | A | ) | = | 280 | A | − | 9 | ( | 500 | − | 220 | ) |
| 4598 | − | 220 | A | − | 200 | × | 209 10 | + | 200 | A | = | 280 | A | − | 9 | ( | 500 | − | 220 | ) |
| 4598 | − | 220 | A | − | 200 | × | 209 10 | + | 200 | A | = | 280 | A | − | 9 | × | 500 | + | 9 | × | 220 |
| 4598 | − | 220 | A | − | 4180 | + | 200 | A | = | 280 | A | − | 4500 | + | 1980 |
| 418 | − | 20 | A | = | 280 | A | − | 2520 |
| - | 20 | A | − | 280 | A | = | - | 2520 | − | 418 |
| - | 300 | A | = | - | 2520 | − | 418 |
| - | 300 | A | = | - | 2938 |
| 2938 | = | 300 | A |
| 300 | A | = | 2938 |
| A | = | 2938 | ÷ | 300 |
| = | 2938 | × | 1 300 |
| = | 1469 | × | 1 150 |
| A | = | 1469 150 |
| A | = | 9.793333 |