| 100 | × | 800 | ( | 1 | − | a | ÷ | 100 | ) | ( | 1 | + | 20 | ÷ | 100 | ) | + | 200 | × | 600 | ( | 1 | − | a | ÷ | 100 | ) | ( | 1 | + | 3 | a | ÷ | 100 | ) | = | 108000 |
| Left side of the equation = | 80000 | ( | 1 | − | a | ÷ | 100 | ) | ( | 1 | + | 20 | ÷ | 100 | ) | + | 120000 | ( | 1 | − | a | ÷ | 100 | ) | ( | 1 | + | 3 | a | ÷ | 100 | ) |
| 80000 | ( | 1 | − | a | ÷ | 100 | ) | ( | 1 | + | 20 | ÷ | 100 | ) | + | 120000 | ( | 1 | − | a | ÷ | 100 | ) | ( | 1 | + | 3 | a | ÷ | 100 | ) | = | 108000 |
| Left side of the equation = | 80000 | × | 1 | ( | 1 | + | 20 | ÷ | 100 | ) | − | 80000 | a | ÷ | 100 | × | ( | 1 | + | 20 | ÷ | 100 | ) | + | 120000 | ( | 1 | − | a | ÷ | 100 | ) | ( | 1 | + | 3 | a | ÷ | 100 | ) |
| = | 80000 | ( | 1 | + | 20 | ÷ | 100 | ) | − | 800 | a | ( | 1 | + | 20 | ÷ | 100 | ) | + | 120000 | ( | 1 | − | a | ÷ | 100 | ) | ( | 1 | + | 3 | a | ÷ | 100 | ) |
| = | 80000 | × | 1 | + | 80000 | × | 20 | ÷ | 100 | − | 800 | a | ( | 1 | + | 20 | ÷ | 100 | ) | + | 120000 | ( | 1 | − | a | ÷ | 100 | ) | ( | 1 | + | 3 | a | ÷ | 100 | ) |
| = | 80000 | + | 16000 | − | 800 | a | ( | 1 | + | 20 | ÷ | 100 | ) | + | 120000 | ( | 1 | − | a | ÷ | 100 | ) | ( | 1 | + | 3 | a | ÷ | 100 | ) |
| = | 96000 | − | 800 | a | ( | 1 | + | 20 | ÷ | 100 | ) | + | 120000 | ( | 1 | − | a | ÷ | 100 | ) | ( | 1 | + | 3 | a | ÷ | 100 | ) |
| = | 96000 | − | 800 | a | × | 1 | − | 800 | a | × | 20 | ÷ | 100 | + | 120000 | ( | 1 | − | a | ÷ | 100 | ) | ( | 1 | + | 3 | a | ÷ | 100 | ) |
| = | 96000 | − | 800 | a | − | 160 | a | + | 120000 | ( | 1 | − | a | ÷ | 100 | ) | ( | 1 | + | 3 | a | ÷ | 100 | ) |
| = | 96000 | − | 960 | a | + | 120000 | ( | 1 | − | a | ÷ | 100 | ) | ( | 1 | + | 3 | a | ÷ | 100 | ) |
| = | 96000 | − | 960 | a | + | 120000 | × | 1 | ( | 1 | + | 3 | a | ÷ | 100 | ) | − | 120000 | a | ÷ | 100 | × | ( | 1 | + | 3 | a | ÷ | 100 | ) |
| = | 96000 | − | 960 | a | + | 120000 | ( | 1 | + | 3 | a | ÷ | 100 | ) | − | 1200 | a | ( | 1 | + | 3 | a | ÷ | 100 | ) |
| = | 96000 | − | 960 | a | + | 120000 | × | 1 | + | 120000 | × | 3 | a | ÷ | 100 | − | 1200 | a | ( | 1 | + | 3 | a | ÷ | 100 | ) |
| = | 96000 | − | 960 | a | + | 120000 | + | 3600 | a | − | 1200 | a | ( | 1 | + | 3 | a | ÷ | 100 | ) |
| = | 216000 | + | 2640 | a | − | 1200 | a | ( | 1 | + | 3 | a | ÷ | 100 | ) |
| = | 216000 | + | 2640 | a | − | 1200 | a | × | 1 | − | 1200 | a | × | 3 | a | ÷ | 100 |
| = | 216000 | + | 2640 | a | − | 1200 | a | − | 36 | a | a |
| = | 216000 | + | 1440 | a | − | 36 | a | a |
| 216000 | + | 1440 | a | − | 36 | a | a | = | 108000 |