5 | y | + | 15 | ( | 1200 | − | y | ) | = | ( | 25 | y | + | 45 | ( | 1200 | − | y | ) | ) | × | 30 100 |
方程左边 = | 5 | y | + | 15 | × | 1200 | − | 15 | y |
= | 5 | y | + | 18000 | − | 15 | y |
= | - | 10 | y | + | 18000 |
- | 10 | y | + | 18000 | = | ( | 25 | y | + | 45 | ( | 1200 | − | y | ) | ) | × | 30 100 |
方程右边 = | 25 | y | × | 30 100 | + | 45 | ( | 1200 | − | y | ) | × | 30 100 |
= | 15 2 | y | + | 27 2 | ( | 1200 | − | y | ) |
= | 15 2 | y | + | 27 2 | × | 1200 | − | 27 2 | y |
= | 15 2 | y | + | 16200 | − | 27 2 | y |
= | - | 6 | y | + | 16200 |
- | 10 | y | + | 18000 | = | - | 6 | y | + | 16200 |
- | 10 | y | + | 6 | y | = | 16200 | − | 18000 |
- | 4 | y | = | 16200 | − | 18000 |
- | 4 | y | = | - | 1800 |
1800 | = | 4 | y |
4 | y | = | 1800 |
y | = | 1800 | ÷ | 4 |
= | 1800 | × | 1 4 |
= | 450 | × | 1 |
y | = | 450 |