| 12 | x | ( | 1 | − | ( | 1 | + | 4 100 | ) | − | ( | 7521 100 | − | 60 | ) | ) | ÷ | 4 100 | = | 139 |
| Left side of the equation = | 300 | x | ( | 1 | − | ( | 1 | + | 4 100 | ) | − | ( | 7521 100 | − | 60 | ) | ) |
| 300 | x | ( | 1 | − | ( | 1 | + | 4 100 | ) | − | ( | 7521 100 | − | 60 | ) | ) | = | 139 |
| Left side of the equation = | 300 | x | × | 1 | − | 300 | x | ( | 1 | + | 4 100 | ) | − | 300 | x | ( | 7521 100 | − | 60 | ) |
| = | 300 | x | − | 300 | x | ( | 1 | + | 4 100 | ) | − | 300 | x | ( | 7521 100 | − | 60 | ) |
| = | 300 | x | − | 300 | x | × | 1 | − | 300 | x | × | 4 100 | − | 300 | x | ( | 7521 100 | − | 60 | ) |
| = | 300 | x | − | 300 | x | − | 12 | x | − | 300 | x | ( | 7521 100 | − | 60 | ) |
| = | - | 12 | x | − | 300 | x | ( | 7521 100 | − | 60 | ) |
| = | - | 12 | x | − | 300 | x | × | 7521 100 | + | 300 | x | × | 60 |
| = | - | 12 | x | − | 22563 | x | + | 18000 | x |
| = | - | 4575 | x |
| - | 4575 | x | = | 139 |
| - | 139 | = | 4575 | x |
| 4575 | x | = | - | 139 |
| x | = | - | 139 | ÷ | 4575 |
| = | - | 139 | × | 1 4575 |
| x | = | - | 139 4575 |
| x | = | - 0.030383 |