| ( | 200 | a | ÷ | 1 20 | + | 500 | ) | ( | 3 10 | − | a | ) | = | 180 |
| Left side of the equation = | 200 | a | ÷ | 1 20 | × | ( | 3 10 | − | a | ) | + | 500 | ( | 3 10 | − | a | ) |
| = | 4000 | a | ( | 3 10 | − | a | ) | + | 500 | ( | 3 10 | − | a | ) |
| = | 4000 | a | × | 3 10 | − | 4000 | a | a | + | 500 | ( | 3 10 | − | a | ) |
| = | 1200 | a | − | 4000 | a | a | + | 500 | ( | 3 10 | − | a | ) |
| = | 1200 | a | − | 4000 | a | a | + | 500 | × | 3 10 | − | 500 | a |
| = | 1200 | a | − | 4000 | a | a | + | 150 | − | 500 | a |
| = | 700 | a | − | 4000 | a | a | + | 150 |
| 700 | a | − | 4000 | a | a | + | 150 | = | 180 |
| a1= | 3 40 |
| a2= | 1 10 |