| 30 | ( | 1 | + | 2 | a | ÷ | 100 | ) | − | 20 | ( | 1 | + | 3 | a | ÷ | 100 | ) | = | 283 25 |
| Left side of the equation = | 30 | × | 1 | + | 30 | × | 2 | a | ÷ | 100 | − | 20 | ( | 1 | + | 3 | a | ÷ | 100 | ) |
| = | 30 | + | 3 5 | a | − | 20 | ( | 1 | + | 3 | a | ÷ | 100 | ) |
| = | 30 | + | 3 5 | a | − | 20 | × | 1 | − | 20 | × | 3 | a | ÷ | 100 |
| = | 30 | + | 3 5 | a | − | 20 | − | 3 5 | a |
| = | 10 | + | 0 | a |
| 10 | + | 0 | a | = | 283 25 |
| = | 283 25 | − | 10 |