| 25 | − | 9 | − | ( | 6 | − | k | ÷ | 6 | ) | ( | 4 | − | k | ÷ | 4 | ) | = | 2 | k |
| Left side of the equation = | 16 | − | ( | 6 | − | k | ÷ | 6 | ) | ( | 4 | − | k | ÷ | 4 | ) |
| 16 | − | ( | 6 | − | k | ÷ | 6 | ) | ( | 4 | − | k | ÷ | 4 | ) | = | 2 | k |
| Left side of the equation = | 16 | − | 6 | ( | 4 | − | k | ÷ | 4 | ) | + | k | ÷ | 6 | × | ( | 4 | − | k | ÷ | 4 | ) |
| = | 16 | − | 6 | × | 4 | + | 6 | k | ÷ | 4 | + | k | × | 1 6 | ( | 4 | − | k | ÷ | 4 | ) |
| = | 16 | − | 24 | + | 3 2 | k | + | k | × | 1 6 | ( | 4 | − | k | ÷ | 4 | ) |
| = | - | 8 | + | 3 2 | k | + | k | × | 1 6 | ( | 4 | − | k | ÷ | 4 | ) |
| = | - | 8 | + | 3 2 | k | + | k | × | 1 6 | × | 4 | − | k | × | 1 6 | k | ÷ | 4 |
| = | - | 8 | + | 3 2 | k | + | k | × | 2 3 | − | k | × | 1 24 | k |
| = | - | 8 | + | 13 6 | k | − | k | × | 1 24 | k |
| - | 8 | + | 13 6 | k | − | k | × | 1 24 | k | = | 2 | k |