| 1 | ÷ | d | + | 1 | ÷ | d | + | 2 | + | 1 | ÷ | d | + | 3 | = | 1 | ÷ | d |
| Multiply both sides of the equation by: | d |
| 1 | + | 1 | ÷ | 1 | × | 1 | + | 2 | d | + | 1 | ÷ | 1 | × | 1 | + | 3 | d | = | 1 | ÷ | 1 | × | 1 |
| 2 | d | + | 3 | d | = | 1 | ÷ | 1 | × | 1 | − | 1 | − | 1 | ÷ | 1 | × | 1 | − | 1 | ÷ | 1 | × | 1 |
| 2 | d | + | 3 | d | = | 1 | − | 1 | − | 1 | − | 1 |
| 5 | d | = | 1 | − | 1 | − | 1 | − | 1 |
| 5 | d | = | - | 2 |
| d | = | - | 2 | ÷ | 5 |
| = | - | 2 | × | 1 5 |
| d | = | - | 2 5 |
| d | = | - 0.4 |