| 7200 | ( | 1 | + | x | ) | ( | 1 | + | x | ) | = | 8450 |
| Left side of the equation = | 7200 | × | 1 | ( | 1 | + | x | ) | + | 7200 | x | ( | 1 | + | x | ) |
| = | 7200 | ( | 1 | + | x | ) | + | 7200 | x | ( | 1 | + | x | ) |
| = | 7200 | × | 1 | + | 7200 | x | + | 7200 | x | ( | 1 | + | x | ) |
| = | 7200 | + | 7200 | x | + | 7200 | x | ( | 1 | + | x | ) |
| = | 7200 | + | 7200 | x | + | 7200 | x | × | 1 | + | 7200 | x | x |
| = | 7200 | + | 7200 | x | + | 7200 | x | + | 7200 | x | x |
| = | 7200 | + | 14400 | x | + | 7200 | x | x |
| 7200 | + | 14400 | x | + | 7200 | x | x | = | 8450 |
| x1= | - | 25 12 |
| x2= | 1 12 |