1 2 | = | ( | 250000 | + | 640000 | − | a | a | ) | ÷ | ( | 2 | × | 500 | × | 800 | ) |
| Multiply both sides of the equation by: | ( | 2 | × | 500 | × | 800 | ) |
1 2 | ( | 2 | × | 500 | × | 800 | ) | = | ( | 250000 | + | 640000 | − | a | a | ) |
1 2 | × | 2 | × | 500 | × | 800 | = | ( | 250000 | + | 640000 | − | a | a | ) |
1 2 | × | 2 | × | 500 | × | 800 | = | 250000 | + | 640000 | − | a | a |
| 400000 | = | 250000 | + | 640000 | − | a | a |
| 400000 | = | 890000 | − | a | a |