| 7 | ( | 5 | X | − | 50 | ) | = | 5 | ( | 5 | X | − | 50 | ) |
| Left side of the equation = | 7 | × | 5 | X | − | 7 | × | 50 |
| = | 35 | X | − | 350 |
| 35 | X | − | 350 | = | 5 | ( | 5 | X | − | 50 | ) |
| Right side of the equation = | 5 | × | 5 | X | − | 5 | × | 50 |
| = | 25 | X | − | 250 |
| 35 | X | − | 350 | = | 25 | X | − | 250 |
| 35 | X | − | 25 | X | = | - | 250 | + | 350 |
| 10 | X | = | - | 250 | + | 350 |
| 10 | X | = | 100 |
| X | = | 100 | ÷ | 10 |
| = | 100 | × | 1 10 |
| = | 10 | × | 1 |
| X | = | 10 |