20 | x | − | ( | 20 | ( | 800 | − | x | ) | ) | − | ( | 60 | ( | 400 | − | x | ) | ) | = | 0 |
方程左边 = | 20 | x | − | 20 | ( | 800 | − | x | ) | − | ( | 60 | ( | 400 | − | x | ) | ) |
= | 20 | x | − | 20 | × | 800 | + | 20 | x | − | ( | 60 | ( | 400 | − | x | ) | ) |
= | 20 | x | − | 16000 | + | 20 | x | − | ( | 60 | ( | 400 | − | x | ) | ) |
= | 40 | x | − | 16000 | − | ( | 60 | ( | 400 | − | x | ) | ) |
= | 40 | x | − | 16000 | − | 60 | ( | 400 | − | x | ) |
= | 40 | x | − | 16000 | − | 60 | × | 400 | + | 60 | x |
= | 40 | x | − | 16000 | − | 24000 | + | 60 | x |
= | 100 | x | − | 40000 |
100 | x | − | 40000 | = | 0 |
100 | x | = | 0 | + | 40000 |
100 | x | = | 40000 |
x | = | 40000 | ÷ | 100 |
= | 40000 | × | 1 100 |
= | 400 | × | 1 |
x | = | 400 |