( | 100 | − | 2 | X | ) | ( | 80 | − | X | ) | = | 608 |
方程左边 = | 100 | ( | 80 | − | X | ) | − | 2 | X | ( | 80 | − | X | ) |
= | 100 | × | 80 | − | 100 | X | − | 2 | X | ( | 80 | − | X | ) |
= | 8000 | − | 100 | X | − | 2 | X | ( | 80 | − | X | ) |
= | 8000 | − | 100 | X | − | 2 | X | × | 80 | + | 2 | X | X |
= | 8000 | − | 100 | X | − | 160 | X | + | 2 | X | X |
= | 8000 | − | 260 | X | + | 2 | X | X |
8000 | − | 260 | X | + | 2 | X | X | = | 608 |