| 30 | + | 10 | x | + | 350 | + | 20 | ( | 55 | − | 6 | − | 7 | ) | = | 1180 |
| 方程左边 = | 380 | + | 10 | x | + | 20 | ( | 55 | − | 6 | − | 7 | ) |
| 380 | + | 10 | x | + | 20 | ( | 55 | − | 6 | − | 7 | ) | = | 1180 |
| 方程左边 = | 380 | + | 10 | x | + | 20 | × | 55 | − | 20 | × | 6 | − | 20 | × | 7 |
| = | 380 | + | 10 | x | + | 1100 | − | 120 | − | 140 |
| = | 1220 | + | 10 | x |
| 1220 | + | 10 | x | = | 1180 |
| 10 | x | = | 1180 | − | 1220 |
| 10 | x | = | - | 40 |
| x | = | - | 40 | ÷ | 10 |
| = | - | 40 | × | 1 10 |
| = | - | 4 | × | 1 |
| x | = | - | 4 |