| ( | 144 | − | b | ) | ÷ | 5 | − | b | ÷ | 2 | = | 40 |
| Left side of the equation = | 144 | × | 1 5 | − | b | × | 1 5 | − | 1 2 | b |
| = | 144 5 | − | b | × | 1 5 | − | 1 2 | b |
| = | 144 5 | − | 7 10 | b |
144 5 | − | 7 10 | b | = | 40 |
| - | 7 10 | b | = | 40 | − | 144 5 |
| - | 7 10 | b | = | 56 5 |
| - | 56 5 | = | 7 10 | b |
7 10 | b | = | - | 56 5 |
| b | = | - | 56 5 | ÷ | 7 10 |
| = | - | 56 5 | × | 10 7 |
| = | - | 8 | × | 2 |
| b | = | - | 16 |