| ( | 21 2 | + | 16 | + | 3 | x | ) | × | 3 | = | ( | 21 2 | + | 11 | + | 3 | x | ) | × | 4 |
| 方程左边 = | 21 2 | × | 3 | + | 16 | × | 3 | + | 3 | x | × | 3 |
| = | 63 2 | + | 48 | + | 9 | x |
| = | 159 2 | + | 9 | x |
159 2 | + | 9 | x | = | ( | 21 2 | + | 11 | + | 3 | x | ) | × | 4 |
| 方程右边 = | 21 2 | × | 4 | + | 11 | × | 4 | + | 3 | x | × | 4 |
| = | 42 | + | 44 | + | 12 | x |
| = | 86 | + | 12 | x |
159 2 | + | 9 | x | = | 86 | + | 12 | x |
| 9 | x | − | 12 | x | = | 86 | − | 159 2 |
| - | 3 | x | = | 86 | − | 159 2 |
| - | 3 | x | = | 13 2 |
| - | 13 2 | = | 3 | x |
| 3 | x | = | - | 13 2 |
| x | = | - | 13 2 | ÷ | 3 |
| = | - | 13 2 | × | 1 3 |
| x | = | - | 13 6 |
| x | = | - 2.166667 |