| ( | a | − | 20 | ) | × | 2 | + | 10 | + | ( | a | − | 20 | ) | = | 118 |
| Left side of the equation = | a | × | 2 | − | 20 | × | 2 | + | 10 | + | ( | a | − | 20 | ) |
| = | a | × | 2 | − | 40 | + | 10 | + | ( | a | − | 20 | ) |
| = | 2 | a | − | 30 | + | ( | a | − | 20 | ) |
| = | 2 | a | − | 30 | + | a | − | 20 |
| = | 3 | a | − | 50 |
| 3 | a | − | 50 | = | 118 |
| 3 | a | = | 118 | + | 50 |
| 3 | a | = | 168 |
| a | = | 168 | ÷ | 3 |
| = | 168 | × | 1 3 |
| = | 56 | × | 1 |
| a | = | 56 |