| ( | 1 | ÷ | 2 | ) | x | + | ( | 30 | − | x | ) | × | 1 | ÷ | 3 | = | 13 |
| 方程左边 = | ( | 1 | ÷ | 2 | ) | x | + | ( | 30 | − | x | ) | × | 1 3 |
| ( | 1 | ÷ | 2 | ) | x | + | ( | 30 | − | x | ) | × | 1 3 | = | 13 |
| 方程左边 = | 1 | ÷ | 2 | × | x | + | ( | 30 | − | x | ) | × | 1 3 |
| = | 1 2 | x | + | ( | 30 | − | x | ) | × | 1 3 |
| = | 1 2 | x | + | 30 | × | 1 3 | − | x | × | 1 3 |
| = | 1 2 | x | + | 10 | − | x | × | 1 3 |
| = | 1 6 | x | + | 10 |
1 6 | x | + | 10 | = | 13 |
1 6 | x | = | 13 | − | 10 |
1 6 | x | = | 3 |
| x | = | 3 | ÷ | 1 6 |
| = | 3 | × | 6 |
| x | = | 18 |