| 20 | ( | ( | 1 | + | x | ) | ( | 1 | + | x | ) | ( | 1 | + | x | ) | ) | + | 10 | ( | 1 | + | x | ) | = | 31 |
| Left side of the equation = | 20 | ( | 1 | + | x | ) | ( | 1 | + | x | ) | ( | 1 | + | x | ) | + | 10 | ( | 1 | + | x | ) |
| = | 20 | × | 1 | ( | 1 | + | x | ) | ( | 1 | + | x | ) | + | 20 | x | ( | 1 | + | x | ) | ( | 1 | + | x | ) | + | 10 | ( | 1 | + | x | ) |
| = | 20 | ( | 1 | + | x | ) | ( | 1 | + | x | ) | + | 20 | x | ( | 1 | + | x | ) | ( | 1 | + | x | ) | + | 10 | ( | 1 | + | x | ) |
| = | 20 | × | 1 | ( | 1 | + | x | ) | + | 20 | x | ( | 1 | + | x | ) | + | 20 | x | ( | 1 | + | x | ) | ( | 1 | + | x | ) | + | 10 | ( | 1 | + | x | ) |
| = | 20 | ( | 1 | + | x | ) | + | 20 | x | ( | 1 | + | x | ) | + | 20 | x | ( | 1 | + | x | ) | ( | 1 | + | x | ) | + | 10 | ( | 1 | + | x | ) |
| = | 20 | × | 1 | + | 20 | x | + | 20 | x | ( | 1 | + | x | ) | + | 20 | x | ( | 1 | + | x | ) | ( | 1 | + | x | ) | + | 10 |
| = | 20 | + | 20 | x | + | 20 | x | ( | 1 | + | x | ) | + | 20 | x | ( | 1 | + | x | ) | ( | 1 | + | x | ) | + | 10 | ( | 1 | + | x | ) |
| = | 20 | + | 20 | x | + | 20 | x | × | 1 | + | 20 | x | x | + | 20 | x | ( | 1 | + | x | ) |
| = | 20 | + | 20 | x | + | 20 | x | + | 20 | x | x | + | 20 | x | ( | 1 | + | x | ) | ( | 1 | + | x | ) |
| = | 20 | + | 40 | x | + | 20 | x | x | + | 20 | x | ( | 1 | + | x | ) | ( | 1 | + | x | ) | + | 10 | ( | 1 | + | x | ) |
| = | 20 | + | 40 | x | + | 20 | x | x | + | 20 | x | × | 1 | ( | 1 | + | x | ) | + | 20 | x |
| = | 20 | + | 40 | x | + | 20 | x | x | + | 20 | x | ( | 1 | + | x | ) | + | 20 | x | x |
| = | 20 | + | 40 | x | + | 20 | x | x | + | 20 | x | × | 1 | + | 20 | x | x |
| = | 20 | + | 40 | x | + | 20 | x | x | + | 20 | x | + | 20 | x | x | + | 20 |
| = | 20 | + | 60 | x | + | 20 | x | x | + | 20 | x | x | + | 20 | x | x |
| = | 20 | + | 60 | x | + | 20 | x | x | + | 20 | x | x | + | 20 | x | x |
| = | 20 | + | 60 | x | + | 20 | x | x | + | 20 | x | x | + | 20 | x | x |
| = | 20 | + | 60 | x | + | 20 | x | x | + | 20 | x | x | + | 20 | x | x |
| = | 20 | + | 60 | x | + | 20 | x | x | + | 20 | x | x | + | 20 | x | x |
| = | 30 | + | 70 | x | + | 20 | x | x | + | 20 | x | x | + | 20 | x | x |
| 30 | + | 70 | x | + | 20 | x | x | + | 20 | x | x | + | 20 | x | x | = | 31 |