| ( | 400 | + | 20 | + | 9 | + | 2 | + | 1 | ) | ÷ | ( | 90 | + | x | ) | = | 24 5 |
| 方程两边同时乘以: | ( | 90 | + | x | ) |
| ( | 400 | + | 20 | + | 9 | + | 2 | + | 1 | ) | = | 24 5 | ( | 90 | + | x | ) |
| 400 | + | 20 | + | 9 | + | 2 | + | 1 | = | 24 5 | ( | 90 | + | x | ) |
| 400 | + | 20 | + | 9 | + | 2 | + | 1 | = | 24 5 | × | 90 | + | 24 5 | x |
| 400 | + | 20 | + | 9 | + | 2 | + | 1 | = | 432 | + | 24 5 | x |
| 432 | = | 432 | + | 24 5 | x |
| - | 24 5 | x | = | 432 | − | 432 |
| - | 24 5 | x | = | 0 |
| - | 0 | = | 24 5 | x |
24 5 | x | = | - | 0 |
| x | = | - | 0 | ÷ | 24 5 |
| = | - | 0 | × | 5 24 |
| x | = | 0 |