| 720 | X | = | 800 | ( | X | − | 3 | ) | + | 1160 |
| Right side of the equation = | 800 | X | − | 800 | × | 3 | + | 1160 |
| = | 800 | X | − | 2400 | + | 1160 |
| = | 800 | X | − | 1240 |
| 720 | X | = | 800 | X | − | 1240 |
| 720 | X | − | 800 | X | = | - | 1240 |
| - | 80 | X | = | - | 1240 |
| 1240 | = | 80 | X |
| 80 | X | = | 1240 |
| X | = | 1240 | ÷ | 80 |
| = | 1240 | × | 1 80 |
| = | 31 | × | 1 2 |
| X | = | 31 2 |
| X | = | 15.5 |