| 7 | + | 8 | ( | 6 | + | 30 | ÷ | ( | - | 2 | x | + | 8 | ) | ) | = | 15 |
| 7 | + | 8 | × | 6 | + | 8 | × | 30 | ÷ | ( | - | 2 | x | + | 8 | ) | = | 15 |
| 7 | + | 48 | + | 240 | ÷ | ( | - | 2 | x | + | 8 | ) | = | 15 |
| 55 | + | 240 | ÷ | ( | - | 2 | x | + | 8 | ) | = | 15 |
| Multiply both sides of the equation by: | ( | - | 2 | x | + | 8 | ) |
| 55 | ( | - | 2 | x | + | 8 | ) | + | 240 | = | 15 | ( | - | 2 | x | + | 8 | ) |
| - | 55 | × | 2 | x | + | 55 | × | 8 | + | 240 | = | 15 | ( | - | 2 | x | + | 8 | ) |
| - | 55 | × | 2 | x | + | 55 | × | 8 | + | 240 | = | - | 15 | × | 2 | x | + | 15 | × | 8 |
| - | 110 | x | + | 440 | + | 240 | = | - | 30 | x | + | 120 |
| - | 110 | x | + | 680 | = | - | 30 | x | + | 120 |
| - | 110 | x | + | 30 | x | = | 120 | − | 680 |
| - | 80 | x | = | 120 | − | 680 |
| - | 80 | x | = | - | 560 |
| 560 | = | 80 | x |
| 80 | x | = | 560 |
| x | = | 560 | ÷ | 80 |
| = | 560 | × | 1 80 |
| = | 7 | × | 1 |
| x | = | 7 |