| - | 12500 | − | ( | 5000 | + | a | ) | × | 12 100 | ÷ | 12 | + | a | = | 5000 |
| Left side of the equation = | - | 12500 | − | ( | 5000 | + | a | ) | × | 1 100 | + | a |
| - | 12500 | − | ( | 5000 | + | a | ) | × | 1 100 | + | a | = | 5000 |
| Left side of the equation = | - | 12500 | − | 5000 | × | 1 100 | − | a | × | 1 100 | + | a |
| = | - | 12500 | − | 50 | − | a | × | 1 100 | + | a |
| = | - | 12550 | + | 99 100 | a |
| - | 12550 | + | 99 100 | a | = | 5000 |
99 100 | a | = | 5000 | + | 12550 |
99 100 | a | = | 17550 |
| a | = | 17550 | ÷ | 99 100 |
| = | 17550 | × | 100 99 |
| = | 1950 | × | 100 11 |
| a | = | 195000 11 |
| a | = | 17727.272727 |