| 42 | ( | 144 | − | x | ) | = | 2 | × | 15 | x |
| Left side of the equation = | 42 | × | 144 | − | 42 | x |
| = | 6048 | − | 42 | x |
| 6048 | − | 42 | x | = | 2 | × | 15 | x |
| Right side of the equation = | 30 | x |
| 6048 | − | 42 | x | = | 30 | x |
| - | 42 | x | − | 30 | x | = | - | 6048 |
| - | 72 | x | = | - | 6048 |
| 6048 | = | 72 | x |
| 72 | x | = | 6048 |
| x | = | 6048 | ÷ | 72 |
| = | 6048 | × | 1 72 |
| = | 84 | × | 1 |
| x | = | 84 |