| 200 | ( | X | − | 3 | ) | = | 120 | ( | X | + | 5 | ) |
| Left side of the equation = | 200 | X | − | 200 | × | 3 |
| = | 200 | X | − | 600 |
| 200 | X | − | 600 | = | 120 | ( | X | + | 5 | ) |
| Right side of the equation = | 120 | X | + | 120 | × | 5 |
| = | 120 | X | + | 600 |
| 200 | X | − | 600 | = | 120 | X | + | 600 |
| 200 | X | − | 120 | X | = | 600 | + | 600 |
| 80 | X | = | 600 | + | 600 |
| 80 | X | = | 1200 |
| X | = | 1200 | ÷ | 80 |
| = | 1200 | × | 1 80 |
| = | 15 | × | 1 |
| X | = | 15 |