| ( | 719 100 | − | 7 10 | − | y | ) | = | ( | y | − | 21 5 | ) | ÷ | 3 |
| 方程左边 = | 719 100 | − | 7 10 | − | y |
| = | 649 100 | − | y |
649 100 | − | y | = | ( | y | − | 21 5 | ) | ÷ | 3 |
| 方程右边 = | y | × | 1 3 | − | 21 5 | × | 1 3 |
| = | y | × | 1 3 | − | 7 5 |
649 100 | − | y | = | 1 3 | y | − | 7 5 |
| - | y | − | 1 3 | y | = | - | 7 5 | − | 649 100 |
| - | 4 3 | y | = | - | 7 5 | − | 649 100 |
| - | 4 3 | y | = | - | 789 100 |
789 100 | = | 4 3 | y |
4 3 | y | = | 789 100 |
| y | = | 789 100 | ÷ | 4 3 |
| = | 789 100 | × | 3 4 |
| y | = | 2367 400 |
| y | = | 5.9175 |