| ( | 200 | + | 1 10 | y | × | 50 | ) | ( | 4 | − | 3 | ( | 1 | − | y | ) | ) | − | 40 | = | 200 |
| 方程左边 = | 200 | ( | 4 | − | 3 | ( | 1 | − | y | ) | ) | + | 1 10 | y | × | 50 | ( | 4 | − | 3 | ( | 1 | − | y | ) | ) | − | 40 |
| = | 200 | ( | 4 | − | 3 | ( | 1 | − | y | ) | ) | + | 5 | y | ( | 4 | − | 3 | ( | 1 | − | y | ) | ) | − | 40 |
| = | 200 | × | 4 | − | 200 | × | 3 | ( | 1 | − | y | ) | + | 5 | y | ( | 4 | − | 3 | ( | 1 | − | y | ) | ) | − | 40 |
| = | 800 | − | 600 | ( | 1 | − | y | ) | + | 5 | y | ( | 4 | − | 3 | ( | 1 | − | y | ) | ) | − | 40 |
| = | 760 | − | 600 | ( | 1 | − | y | ) | + | 5 | y | ( | 4 | − | 3 | ( | 1 | − | y | ) | ) |
| = | 760 | − | 600 | × | 1 | + | 600 | y | + | 5 | y | ( | 4 | − | 3 | ( | 1 | − | y | ) | ) |
| = | 760 | − | 600 | + | 600 | y | + | 5 | y | ( | 4 | − | 3 | ( | 1 | − | y | ) | ) |
| = | 160 | + | 600 | y | + | 5 | y | ( | 4 | − | 3 | ( | 1 | − | y | ) | ) |
| = | 160 | + | 600 | y | + | 5 | y | × | 4 | − | 5 | y | × | 3 | ( | 1 | − | y | ) |
| = | 160 | + | 600 | y | + | 20 | y | − | 15 | y | ( | 1 | − | y | ) |
| = | 160 | + | 620 | y | − | 15 | y | ( | 1 | − | y | ) |
| = | 160 | + | 620 | y | − | 15 | y | × | 1 | + | 15 | y | y |
| = | 160 | + | 620 | y | − | 15 | y | + | 15 | y | y |
| = | 160 | + | 605 | y | + | 15 | y | y |
| 160 | + | 605 | y | + | 15 | y | y | = | 200 |