| ( | 80 | − | 4 | x | ) | ( | 10 | + | ( | x | − | 1 | ) | × | 2 | ) | = | 1080 |
| Left side of the equation = | 80 | ( | 10 | + | ( | x | − | 1 | ) | × | 2 | ) | − | 4 | x | ( | 10 | + | ( | x | − | 1 | ) | × | 2 | ) |
| = | 80 | × | 10 | + | 80 | ( | x | − | 1 | ) | × | 2 | − | 4 | x | ( | 10 | + | ( | x | − | 1 | ) | × | 2 | ) |
| = | 800 | + | 160 | ( | x | − | 1 | ) | − | 4 | x | ( | 10 | + | ( | x | − | 1 | ) | × | 2 | ) |
| = | 800 | + | 160 | x | − | 160 | × | 1 | − | 4 | x | ( | 10 | + | ( | x | − | 1 | ) | × | 2 | ) |
| = | 800 | + | 160 | x | − | 160 | − | 4 | x | ( | 10 | + | ( | x | − | 1 | ) | × | 2 | ) |
| = | 640 | + | 160 | x | − | 4 | x | ( | 10 | + | ( | x | − | 1 | ) | × | 2 | ) |
| = | 640 | + | 160 | x | − | 4 | x | × | 10 | − | 4 | x | ( | x | − | 1 | ) | × | 2 |
| = | 640 | + | 160 | x | − | 40 | x | − | 8 | x | ( | x | − | 1 | ) |
| = | 640 | + | 120 | x | − | 8 | x | ( | x | − | 1 | ) |
| = | 640 | + | 120 | x | − | 8 | x | x | + | 8 | x | × | 1 |
| = | 640 | + | 120 | x | − | 8 | x | x | + | 8 | x |
| = | 640 | + | 128 | x | − | 8 | x | x |
| 640 | + | 128 | x | − | 8 | x | x | = | 1080 |