| ( | 50000 | ( | 1 | + | 21 200 | ) | + | y | ) | × | 12 100 | = | 50000 | × | 21 200 | + | 3000 |
| 方程左边 = | 50000 | ( | 1 | + | 21 200 | ) | × | 12 100 | + | y | × | 12 100 |
| = | 6000 | ( | 1 | + | 21 200 | ) | + | y | × | 12 100 |
| = | 6000 | × | 1 | + | 6000 | × | 21 200 | + | 12 100 | y |
| = | 6000 | + | 630 | + | 12 100 | y |
| = | 6630 | + | 12 100 | y |
| 6630 | + | 12 100 | y | = | 50000 | × | 21 200 | + | 3000 |
| 方程右边 = | 5250 | + | 3000 |
| = | 8250 |
| 6630 | + | 12 100 | y | = | 8250 |
12 100 | y | = | 8250 | − | 6630 |
12 100 | y | = | 1620 |
| y | = | 1620 | ÷ | 12 100 |
| = | 1620 | × | 100 12 |
| = | 135 | × | 100 |
| y | = | 13500 |