| ( | a | + | 45 | ) | × | 8 | × | 17 20 | − | 8 | a | = | 120 |
| Left side of the equation = | ( | a | + | 45 | ) | × | 34 5 | − | 8 | a |
| ( | a | + | 45 | ) | × | 34 5 | − | 8 | a | = | 120 |
| Left side of the equation = | a | × | 34 5 | + | 45 | × | 34 5 | − | 8 | a |
| = | a | × | 34 5 | + | 306 | − | 8 | a |
| = | - | 6 5 | a | + | 306 |
| - | 6 5 | a | + | 306 | = | 120 |
| - | 6 5 | a | = | 120 | − | 306 |
| - | 6 5 | a | = | - | 186 |
| 186 | = | 6 5 | a |
6 5 | a | = | 186 |
| a | = | 186 | ÷ | 6 5 |
| = | 186 | × | 5 6 |
| = | 31 | × | 5 |
| a | = | 155 |