| a | × | 2 | + | ( | 100 | − | a | ) | × | 2 | = | ( | 200 | − | 2 | a | ) | × | 2 |
| Left side of the equation = | 2 | a | + | 100 | × | 2 | − | a | × | 2 |
| = | 2 | a | + | 200 | − | a | × | 2 |
| = | 0 | a | + | 200 |
| 0 | a | + | 200 | = | ( | 200 | − | 2 | a | ) | × | 2 |
| Right side of the equation = | 200 | × | 2 | − | 2 | a | × | 2 |
| = | 400 | − | 4 | a |
| 200 | = | 400 | − | 4 | a |
| 4 | a | = | 400 | − | 200 |
| 4 | a | = | 200 |
| a | = | 200 | ÷ | 4 |
| = | 200 | × | 1 4 |
| = | 50 | × | 1 |
| a | = | 50 |