| ( | 20 | X | ) | + | 25 | ( | 80 | − | X | ) | = | 1700 |
| Left side of the equation = | 20 | X | + | 25 | ( | 80 | − | X | ) |
| = | 20 | X | + | 25 | × | 80 | − | 25 | X |
| = | 20 | X | + | 2000 | − | 25 | X |
| = | - | 5 | X | + | 2000 |
| - | 5 | X | + | 2000 | = | 1700 |
| - | 5 | X | = | 1700 | − | 2000 |
| - | 5 | X | = | - | 300 |
| 300 | = | 5 | X |
| 5 | X | = | 300 |
| X | = | 300 | ÷ | 5 |
| = | 300 | × | 1 5 |
| = | 60 | × | 1 |
| X | = | 60 |