| 10 | × | 20 | − | ( | 10 | − | x | ) | × | 12 | = | 136 |
| Left side of the equation = | 200 | − | ( | 10 | − | x | ) | × | 12 |
| 200 | − | ( | 10 | − | x | ) | × | 12 | = | 136 |
| Left side of the equation = | 200 | − | 10 | × | 12 | + | x | × | 12 |
| = | 200 | − | 120 | + | x | × | 12 |
| = | 80 | + | 12 | x |
| 80 | + | 12 | x | = | 136 |
| 12 | x | = | 136 | − | 80 |
| 12 | x | = | 56 |
| x | = | 56 | ÷ | 12 |
| = | 56 | × | 1 12 |
| = | 14 | × | 1 3 |
| x | = | 14 3 |
| x | = | 4.666667 |