| 30 | ( | 1 | + | x | ) | ( | 1 | + | x | ) | = | 507 10 |
| Left side of the equation = | 30 | × | 1 | ( | 1 | + | x | ) | + | 30 | x | ( | 1 | + | x | ) |
| = | 30 | ( | 1 | + | x | ) | + | 30 | x | ( | 1 | + | x | ) |
| = | 30 | × | 1 | + | 30 | x | + | 30 | x | ( | 1 | + | x | ) |
| = | 30 | + | 30 | x | + | 30 | x | ( | 1 | + | x | ) |
| = | 30 | + | 30 | x | + | 30 | x | × | 1 | + | 30 | x | x |
| = | 30 | + | 30 | x | + | 30 | x | + | 30 | x | x |
| = | 30 | + | 60 | x | + | 30 | x | x |
| 30 | + | 60 | x | + | 30 | x | x | = | 507 10 |
| x1= | - | 23 10 |
| x2= | 3 10 |