| ( | 800 | − | 500 | ) | ÷ | ( | 1000 | − | 800 | ) | = | ( | A | − | 33 2 | ) | ÷ | ( | 301 10 | − | A | ) |
| 方程两边同时乘以: | ( | 1000 | − | 800 | ) | , | ( | 301 10 | − | A | ) |
| ( | 800 | − | 500 | ) | ( | 301 10 | − | A | ) | = | ( | A | − | 33 2 | ) | ( | 1000 | − | 800 | ) |
| 800 | ( | 301 10 | − | A | ) | − | 500 | ( | 301 10 | − | A | ) | = | ( | A | − | 33 2 | ) | ( | 1000 | − | 800 | ) |
| 800 | ( | 301 10 | − | A | ) | − | 500 | ( | 301 10 | − | A | ) | = | A | ( | 1000 | − | 800 | ) | − | 33 2 | ( | 1000 | − | 800 | ) |
| 800 | × | 301 10 | − | 800 | A | − | 500 | ( | 301 10 | − | A | ) | = | A | ( | 1000 | − | 800 | ) | − | 33 2 | ( | 1000 | − | 800 | ) |
| 800 | × | 301 10 | − | 800 | A | − | 500 | ( | 301 10 | − | A | ) | = | A | × | 1000 | − | A | × | 800 | − | 33 2 | ( | 1000 | − | 800 | ) |
| 24080 | − | 800 | A | − | 500 | ( | 301 10 | − | A | ) | = | A | × | 1000 | − | A | × | 800 | − | 33 2 | ( | 1000 | − | 800 | ) |
| 24080 | − | 800 | A | − | 500 | ( | 301 10 | − | A | ) | = | 200 | A | − | 33 2 | ( | 1000 | − | 800 | ) |
| 24080 | − | 800 | A | − | 500 | × | 301 10 | + | 500 | A | = | 200 | A | − | 33 2 | ( | 1000 | − | 800 | ) |
| 24080 | − | 800 | A | − | 500 | × | 301 10 | + | 500 | A | = | 200 | A | − | 33 2 | × | 1000 | + | 33 2 | × | 800 |
| 24080 | − | 800 | A | − | 15050 | + | 500 | A | = | 200 | A | − | 16500 | + | 13200 |
| 9030 | − | 300 | A | = | 200 | A | − | 3300 |
| - | 300 | A | − | 200 | A | = | - | 3300 | − | 9030 |
| - | 500 | A | = | - | 3300 | − | 9030 |
| - | 500 | A | = | - | 12330 |
| 12330 | = | 500 | A |
| 500 | A | = | 12330 |
| A | = | 12330 | ÷ | 500 |
| = | 12330 | × | 1 500 |
| = | 1233 | × | 1 50 |
| A | = | 1233 50 |
| A | = | 24.66 |