| x | = | 7800000 | − | ( | 10 | × | 40 | × | 4 | ) | ÷ | ( | ( | 40 | + | 4 | ) | × | 10 | ) |
| 方程两边同时乘以: | ( | ( | 40 | + | 4 | ) | × | 10 | ) |
| x | ( | ( | 40 | + | 4 | ) | × | 10 | ) | = | 7800000 | ( | ( | 40 | + | 4 | ) | × | 10 | ) | − | ( | 10 | × | 40 | × | 4 | ) |
| x | ( | 40 | + | 4 | ) | × | 10 | = | 7800000 | ( | ( | 40 | + | 4 | ) | × | 10 | ) | − | ( | 10 | × | 40 | × | 4 | ) |
| x | ( | 40 | + | 4 | ) | × | 10 | = | 7800000 | ( | 40 | + | 4 | ) | × | 10 | − | ( | 10 | × | 40 | × | 4 | ) |
| x | ( | 40 | + | 4 | ) | × | 10 | = | 78000000 | ( | 40 | + | 4 | ) | − | ( | 10 | × | 40 | × | 4 | ) |
| x | × | 40 | × | 10 | + | x | × | 4 | × | 10 | = | 78000000 | ( | 40 | + | 4 | ) | − | ( | 10 | × | 40 | × | 4 | ) |
| x | × | 40 | × | 10 | + | x | × | 4 | × | 10 | = | 78000000 | × | 40 | + | 78000000 | × | 4 | − | ( | 10 | × | 40 | × | 4 | ) |
| x | × | 400 | + | x | × | 40 | = | 3120000000 | + | 312000000 | − | ( | 10 | × | 40 | × | 4 | ) |
| 440 | x | = | 3432000000 | − | ( | 10 | × | 40 | × | 4 | ) |
| 440 | x | = | 3432000000 | − | 10 | × | 40 | × | 4 |
| 440 | x | = | 3432000000 | − | 1600 |
| 440 | x | = | 3431998400 |
| x | = | 3431998400 | ÷ | 440 |
| = | 3431998400 | × | 1 440 |
| = | 85799960 | × | 1 11 |
| x | = | 85799960 11 |
| x | = | 7799996.363636 |