| a | × | 600 | × | 19 20 | + | ( | 20 | − | a | ) | × | 600 | = | 10720 |
| Left side of the equation = | a | × | 570 | + | ( | 20 | − | a | ) | × | 600 |
| 570 | a | + | ( | 20 | − | a | ) | × | 600 | = | 10720 |
| Left side of the equation = | 570 | a | + | 20 | × | 600 | − | a | × | 600 |
| = | 570 | a | + | 12000 | − | a | × | 600 |
| = | - | 30 | a | + | 12000 |
| - | 30 | a | + | 12000 | = | 10720 |
| - | 30 | a | = | 10720 | − | 12000 |
| - | 30 | a | = | - | 1280 |
| 1280 | = | 30 | a |
| 30 | a | = | 1280 |
| a | = | 1280 | ÷ | 30 |
| = | 1280 | × | 1 30 |
| = | 128 | × | 1 3 |
| a | = | 128 3 |
| a | = | 42.666667 |