| 180 | x | + | 300 | ( | 13 | − | x | ) | = | 2850 |
| Left side of the equation = | 180 | x | + | 300 | × | 13 | − | 300 | x |
| = | 180 | x | + | 3900 | − | 300 | x |
| = | - | 120 | x | + | 3900 |
| - | 120 | x | + | 3900 | = | 2850 |
| - | 120 | x | = | 2850 | − | 3900 |
| - | 120 | x | = | - | 1050 |
| 1050 | = | 120 | x |
| 120 | x | = | 1050 |
| x | = | 1050 | ÷ | 120 |
| = | 1050 | × | 1 120 |
| = | 35 | × | 1 4 |
| x | = | 35 4 |
| x | = | 8.75 |