| 1 | ÷ | d | + | 1 | ÷ | d | + | 3 | + | 1 | ÷ | d | + | 5 | = | 1 | ÷ | d | + | 7 |
| Multiply both sides of the equation by: | d |
| 1 | + | 1 | ÷ | 1 | × | 1 | + | 3 | d | + | 1 | ÷ | 1 | × | 1 | + | 5 | d | = | 1 | ÷ | 1 | × | 1 | + | 7 | d |
| 3 | d | + | 5 | d | − | 7 | d | = | 1 | ÷ | 1 | × | 1 | − | 1 | − | 1 | ÷ | 1 | × | 1 | − | 1 | ÷ | 1 | × | 1 |
| 3 | d | + | 5 | d | − | 7 | d | = | 1 | − | 1 | − | 1 | − | 1 |
| d | = | 1 | − | 1 | − | 1 | − | 1 |
| d | = | 1 | − | 1 | − | 1 | − | 1 |
| d | = | - | 2 |