| 278 | ( | x | − | 3 | ) | − | 463 | ( | 6 | − | 2 | x | ) | − | 888 | ( | 7 | x | − | 21 | ) | = | 0 |
| Left side of the equation = | 278 | x | − | 278 | × | 3 | − | 463 | ( | 6 | − | 2 | x | ) | − | 888 | ( | 7 | x | − | 21 | ) |
| = | 278 | x | − | 834 | − | 463 | ( | 6 | − | 2 | x | ) | − | 888 | ( | 7 | x | − | 21 | ) |
| = | 278 | x | − | 834 | − | 463 | × | 6 | + | 463 | × | 2 | x | − | 888 | ( | 7 | x | − | 21 | ) |
| = | 278 | x | − | 834 | − | 2778 | + | 926 | x | − | 888 | ( | 7 | x | − | 21 | ) |
| = | 1204 | x | − | 3612 | − | 888 | ( | 7 | x | − | 21 | ) |
| = | 1204 | x | − | 3612 | − | 888 | × | 7 | x | + | 888 | × | 21 |
| = | 1204 | x | − | 3612 | − | 6216 | x | + | 18648 |
| = | - | 5012 | x | + | 15036 |
| - | 5012 | x | + | 15036 | = | 0 |
| - | 5012 | x | = | 0 | − | 15036 |
| - | 5012 | x | = | - | 15036 |
| 15036 | = | 5012 | x |
| 5012 | x | = | 15036 |
| x | = | 15036 | ÷ | 5012 |
| = | 15036 | × | 1 5012 |
| = | 537 | × | 1 179 |
| x | = | 537 179 |
| x | = | 3 |