| 20 | ( | 1 | + | 2 100 | a | ) | × | 20 | × | 5 2 | × | 3 1000 | a | + | 5 | ( | 1 | + | 6 100 | a | ) | × | 20 | × | 4 | × | 1 400 | a | = | ( | 20 | ( | 1 | + | 2 100 | a | ) | × | 20 | × | 5 2 | + | 5 | ( | 1 | + | 6 100 | a | ) | × | 20 | × | 4 | ) | × | 5 | ÷ | 18 | × | a% |
| 方程左边 = | 3 | ( | 1 | + | 2 100 | a | ) | a | + | 1 | ( | 1 | + | 6 100 | a | ) | a |
| 3 | ( | 1 | + | 2 100 | a | ) | a | + | 1 | ( | 1 | + | 6 100 | a | ) | a | = | ( | 20 | ( | 1 | + | 2 100 | a | ) | × | 20 | × | 5 2 | + | 5 | ( | 1 | + | 6 100 | a | ) | × | 20 | × | 4 | ) | × | 5 | ÷ | 18 | × | a% |
| 方程左边 = | 3 | × | 1 | a | + | 3 | × | 2 100 | a | a | + | 1 | ( | 1 | + | 6 100 | a | ) | a |
| = | 3 | a | + | 3 50 | a | a | + | 1 | ( | 1 | + | 6 100 | a | ) | a |
| = | 3 | a | + | 3 50 | a | a | + | 1 | × | 1 | a | + | 1 | × | 6 100 | a | a |
| = | 3 | a | + | 3 50 | a | a | + | 1 | a | + | 3 50 | a | a |
| = | 4 | a | + | 3 50 | a | a | + | 3 50 | a | a |
| 4 | a | + | 3 50 | a | a | + | 3 50 | a | a | = | ( | 20 | ( | 1 | + | 2 100 | a | ) | × | 20 | × | 5 2 | + | 5 | ( | 1 | + | 6 100 | a | ) | × | 20 | × | 4 | ) | × | 5 | ÷ | 18 | × | a% |
| 方程右边 = | ( | 20 | ( | 1 | + | 2 100 | a | ) | × | 20 | × | 5 2 | + | 5 | ( | 1 | + | 6 100 | a | ) | × | 20 | × | 4 | ) | × | 1 360 | a |
| 4 | a | + | 3 50 | a | a | + | 3 50 | a | a | = | ( | 20 | ( | 1 | + | 2 100 | a | ) | × | 20 | × | 5 2 | + | 5 | ( | 1 | + | 6 100 | a | ) | × | 20 | × | 4 | ) | × | 1 360 | a |
| 方程右边 = | 20 | ( | 1 | + | 2 100 | a | ) | × | 20 | × | 5 2 | × | 1 360 | a | + | 5 | ( | 1 | + | 6 100 | a | ) | × | 20 | × | 4 | × | 1 360 | a |
| = | 25 9 | ( | 1 | + | 2 100 | a | ) | a | + | 10 9 | ( | 1 | + | 6 100 | a | ) | a |
| = | 25 9 | × | 1 | a | + | 25 9 | × | 2 100 | a | a | + | 10 9 | ( | 1 | + | 6 100 | a | ) | a |
| = | 25 9 | a | + | 1 18 | a | a | + | 10 9 | ( | 1 | + | 6 100 | a | ) | a |
| = | 25 9 | a | + | 1 18 | a | a | + | 10 9 | × | 1 | a | + | 10 9 | × | 6 100 | a | a |
| = | 25 9 | a | + | 1 18 | a | a | + | 10 9 | a | + | 1 15 | a | a |
| = | 35 9 | a | + | 1 18 | a | a | + | 1 15 | a | a |
| 4 | a | + | 3 50 | a | a | + | 3 50 | a | a | = | 35 9 | a | + | 1 18 | a | a | + | 1 15 | a | a |