| 19 | ÷ | ( | - | 12 | − | ( | 5 | x | + | 7 | ) | ) | + | 4 | = | 3 |
| 方程两边同时乘以: | ( | - | 12 | − | ( | 5 | x | + | 7 | ) | ) |
| 19 | + | 4 | ( | - | 12 | − | ( | 5 | x | + | 7 | ) | ) | = | 3 | ( | - | 12 | − | ( | 5 | x | + | 7 | ) | ) |
| 19 | − | 4 | × | 12 | − | 4 | ( | 5 | x | + | 7 | ) | = | 3 | ( | - | 12 | − | ( | 5 | x | + | 7 | ) | ) |
| 19 | − | 4 | × | 12 | − | 4 | ( | 5 | x | + | 7 | ) | = | - | 3 | × | 12 | − | 3 | ( | 5 | x | + | 7 | ) |
| 19 | − | 48 | − | 4 | ( | 5 | x | + | 7 | ) | = | - | 36 | − | 3 | ( | 5 | x | + | 7 | ) |
| - | 29 | − | 4 | ( | 5 | x | + | 7 | ) | = | - | 36 | − | 3 | ( | 5 | x | + | 7 | ) |
| - | 29 | − | 4 | × | 5 | x | − | 4 | × | 7 | = | - | 36 | − | 3 | ( | 5 | x | + | 7 | ) |
| - | 29 | − | 4 | × | 5 | x | − | 4 | × | 7 | = | - | 36 | − | 3 | × | 5 | x | − | 3 | × | 7 |
| - | 29 | − | 20 | x | − | 28 | = | - | 36 | − | 15 | x | − | 21 |
| - | 57 | − | 20 | x | = | - | 57 | − | 15 | x |
| - | 20 | x | + | 15 | x | = | - | 57 | + | 57 |
| - | 5 | x | = | - | 57 | + | 57 |
| - | 5 | x | = | - | 0 |
| 0 | = | 5 | x |
| 5 | x | = | 0 |
| x | = | 0 | ÷ | 5 |
| = | 0 | × | 1 5 |
| x | = | 0 |