| a | × | 4 | + | ( | a | + | 3 | ) | × | 2 | − | ( | a | + | 3 | + | a | ) | × | 2 | = | 16 |
| 方程左边 = | 4 | a | + | a | × | 2 | + | 3 | × | 2 | − | ( | a | + | 3 | + | a | ) | × | 2 |
| = | 4 | a | + | a | × | 2 | + | 6 | − | ( | a | + | 3 | + | a | ) | × | 2 |
| = | 6 | a | + | 6 | − | ( | a | + | 3 | + | a | ) | × | 2 |
| = | 6 | a | + | 6 | − | a | × | 2 | − | 3 | × | 2 | − | a | × | 2 |
| = | 6 | a | + | 6 | − | a | × | 2 | − | 6 | − | a | × | 2 |
| = | 2 | a | + | 0 |
| 2 | a | = | 16 |
| a | = | 16 | ÷ | 2 |
| = | 16 | × | 1 2 |
| = | 8 | × | 1 |
| a | = | 8 |