( | 200 | + | 50 | x | ) | ( | 20 | - | 12 | - | x | ) | = | 1750 |
方程左边 = | 200 | ( | 20 | - | 12 | - | x | ) | + | 50 | x | ( | 20 | - | 12 | - | x | ) |
= | 200 | × | 20 | - | 200 | × | 12 | - | 200 | x | + | 50 | x | ( | 20 | - | 12 | - | x | ) |
= | 4000 | - | 2400 | - | 200 | x | + | 50 | x | ( | 20 | - | 12 | - | x | ) |
= | 1600 | - | 200 | x | + | 50 | x | ( | 20 | - | 12 | - | x | ) |
= | 1600 | - | 200 | x | + | 50 | x | × | 20 | - | 50 | x | × | 12 | - | 50 | x | x |
= | 1600 | - | 200 | x | + | 1000 | x | - | 600 | x | - | 50 | x | x |
= | 1600 | + | 200 | x | - | 50 | x | x |
1600 | + | 200 | x | - | 50 | x | x | = | 1750 |