| 492 | − | ( | 6 | − | 5 | x | ) | × | 42 | − | 4 5 | × | 8 | ( | 30 | + | 50 | x | ) | = | 15 |
| 方程左边 = | 492 | − | ( | 6 | − | 5 | x | ) | × | 42 | − | 32 5 | ( | 30 | + | 50 | x | ) |
| 492 | − | ( | 6 | − | 5 | x | ) | × | 42 | − | 32 5 | ( | 30 | + | 50 | x | ) | = | 15 |
| 方程左边 = | 492 | − | 6 | × | 42 | + | 5 | x | × | 42 | − | 32 5 | ( | 30 | + | 50 | x | ) |
| = | 492 | − | 252 | + | 210 | x | − | 32 5 | ( | 30 | + | 50 | x | ) |
| = | 240 | + | 210 | x | − | 32 5 | ( | 30 | + | 50 | x | ) |
| = | 240 | + | 210 | x | − | 32 5 | × | 30 | − | 32 5 | × | 50 | x |
| = | 240 | + | 210 | x | − | 192 | − | 320 | x |
| = | 48 | − | 110 | x |
| 48 | − | 110 | x | = | 15 |
| - | 110 | x | = | 15 | − | 48 |
| - | 110 | x | = | - | 33 |
| 33 | = | 110 | x |
| 110 | x | = | 33 |
| x | = | 33 | ÷ | 110 |
| = | 33 | × | 1 110 |
| = | 3 | × | 1 10 |
| x | = | 3 10 |
| x | = | 0.3 |