11 20 | × | 180 | + | 3 5 | ( | y | − | 180 | ) | + | 180 | × | 11 20 | + | 3 5 | ( | 400 | − | 180 | ) | + | 17 20 | ( | 800 | − | y | − | 400 | ) | = | 482 |
| 方程左边 = | 99 | + | 3 5 | ( | y | − | 180 | ) | + | 99 | + | 3 5 | ( | 400 | − | 180 | ) | + | 17 20 | ( | 800 | − | y | − | 400 | ) |
| = | 198 | + | 3 5 | ( | y | − | 180 | ) | + | 3 5 | ( | 400 | − | 180 | ) | + | 17 20 | ( | 800 | − | y | − | 400 | ) |
| 198 | + | 3 5 | ( | y | − | 180 | ) | + | 3 5 | ( | 400 | − | 180 | ) | + | 17 20 | ( | 800 | − | y | − | 400 | ) | = | 482 |
| 方程左边 = | 198 | + | 3 5 | y | − | 3 5 | × | 180 | + | 3 5 | ( | 400 | − | 180 | ) | + | 17 20 | ( | 800 | − | y | − | 400 | ) |
| = | 198 | + | 3 5 | y | − | 108 | + | 3 5 | ( | 400 | − | 180 | ) | + | 17 20 | ( | 800 | − | y | − | 400 | ) |
| = | 90 | + | 3 5 | y | + | 3 5 | ( | 400 | − | 180 | ) | + | 17 20 | ( | 800 | − | y | − | 400 | ) |
| = | 90 | + | 3 5 | y | + | 3 5 | × | 400 | − | 3 5 | × | 180 | + | 17 20 | ( | 800 | − | y | − | 400 | ) |
| = | 90 | + | 3 5 | y | + | 240 | − | 108 | + | 17 20 | ( | 800 | − | y | − | 400 | ) |
| = | 222 | + | 3 5 | y | + | 17 20 | ( | 800 | − | y | − | 400 | ) |
| = | 222 | + | 3 5 | y | + | 17 20 | × | 800 | − | 17 20 | y | − | 17 20 | × | 400 |
| = | 222 | + | 3 5 | y | + | 680 | − | 17 20 | y | − | 340 |
| = | 562 | − | 1 4 | y |
| 562 | − | 1 4 | y | = | 482 |
| - | 1 4 | y | = | 482 | − | 562 |
| - | 1 4 | y | = | - | 80 |
| 80 | = | 1 4 | y |
1 4 | y | = | 80 |
| y | = | 80 | ÷ | 1 4 |
| = | 80 | × | 4 |
| y | = | 320 |