| 120 | × | 200 | ( | 1 | + | 2 | a | ) | × | 9 10 | + | 80 | × | 150 | ( | 1 | + | a | ) | − | 120 | × | 200 | − | 80 | × | 150 | = | 14160 |
| Left side of the equation = | 21600 | ( | 1 | + | 2 | a | ) | + | 12000 | ( | 1 | + | a | ) | − | 24000 | − | 12000 |
| = | 21600 | ( | 1 | + | 2 | a | ) | + | 12000 | ( | 1 | + | a | ) | − | 36000 |
| 21600 | ( | 1 | + | 2 | a | ) | + | 12000 | ( | 1 | + | a | ) | − | 36000 | = | 14160 |
| Left side of the equation = | 21600 | × | 1 | + | 21600 | × | 2 | a | + | 12000 | ( | 1 | + | a | ) | − | 36000 |
| = | 21600 | + | 43200 | a | + | 12000 | ( | 1 | + | a | ) | − | 36000 |
| = | - | 14400 | + | 43200 | a | + | 12000 | ( | 1 | + | a | ) |
| = | - | 14400 | + | 43200 | a | + | 12000 | × | 1 | + | 12000 | a |
| = | - | 14400 | + | 43200 | a | + | 12000 | + | 12000 | a |
| = | - | 2400 | + | 55200 | a |
| - | 2400 | + | 55200 | a | = | 14160 |
| 55200 | a | = | 14160 | + | 2400 |
| 55200 | a | = | 16560 |
| a | = | 16560 | ÷ | 55200 |
| = | 16560 | × | 1 55200 |
| = | 3 | × | 1 10 |
| a | = | 3 10 |
| a | = | 0.3 |