| ( | 30 | + | 5 | x | ) | ( | 44 | − | 2 | x | ) | = | 0 |
| 方程左边 = | 30 | ( | 44 | − | 2 | x | ) | + | 5 | x | ( | 44 | − | 2 | x | ) |
| = | 30 | × | 44 | − | 30 | × | 2 | x | + | 5 | x | ( | 44 | − | 2 | x | ) |
| = | 1320 | − | 60 | x | + | 5 | x | ( | 44 | − | 2 | x | ) |
| = | 1320 | − | 60 | x | + | 5 | x | × | 44 | − | 5 | x | × | 2 | x |
| = | 1320 | − | 60 | x | + | 220 | x | − | 10 | x | x |
| = | 1320 | + | 160 | x | − | 10 | x | x |
| 1320 | + | 160 | x | − | 10 | x | x | = | 0 |