| 30000 | ( | 1 | + | a | ÷ | 100 | ) | ( | 1 | − | a | ÷ | 100 | × | 9 | ÷ | 10 | ) | = | 20000 |
| Left side of the equation = | 30000 | × | 1 | ( | 1 | − | a | ÷ | 100 | × | 9 | ÷ | 10 | ) | + | 30000 | a | ÷ | 100 | × | ( | 1 | − | a | ÷ | 100 | × | 9 | ÷ | 10 | ) |
| = | 30000 | ( | 1 | − | a | ÷ | 100 | × | 9 | ÷ | 10 | ) | + | 300 | a | ( | 1 | − | a | ÷ | 100 | × | 9 | ÷ | 10 | ) |
| = | 30000 | × | 1 | − | 30000 | a | ÷ | 100 | × | 9 | ÷ | 10 | + | 300 | a | ( | 1 | − | a | ÷ | 100 | × | 9 | ÷ | 10 | ) |
| = | 30000 | − | 270 | a | + | 300 | a | ( | 1 | − | a | ÷ | 100 | × | 9 | ÷ | 10 | ) |
| = | 30000 | − | 270 | a | + | 300 | a | × | 1 | − | 300 | a | a | ÷ | 100 | × | 9 | ÷ | 10 |
| = | 30000 | − | 270 | a | + | 300 | a | − | 27 10 | a | a |
| = | 30000 | + | 30 | a | − | 27 10 | a | a |
| 30000 | + | 30 | a | − | 27 10 | a | a | = | 20000 |
| a1= | - | 500 9 |
| a2= | 200 3 |