| ( | 40000 | − | 2400 | × | 3 | ) | ÷ | ( | 210 | + | x | ) | = | 142 |
| Multiply both sides of the equation by: | ( | 210 | + | x | ) |
| ( | 40000 | − | 2400 | × | 3 | ) | = | 142 | ( | 210 | + | x | ) |
| 40000 | − | 2400 | × | 3 | = | 142 | ( | 210 | + | x | ) |
| 40000 | − | 2400 | × | 3 | = | 142 | × | 210 | + | 142 | x |
| 40000 | − | 7200 | = | 29820 | + | 142 | x |
| 32800 | = | 29820 | + | 142 | x |
| - | 142 | x | = | 29820 | − | 32800 |
| - | 142 | x | = | - | 2980 |
| 2980 | = | 142 | x |
| 142 | x | = | 2980 |
| x | = | 2980 | ÷ | 142 |
| = | 2980 | × | 1 142 |
| = | 1490 | × | 1 71 |
| x | = | 1490 71 |
| x | = | 20.985915 |