| 60 | = | 155 | ÷ | ( | 1 | + | r | ) | − | 100 | ÷ | ( | 1 | + | r | ) |
| Multiply both sides of the equation by: | ( | 1 | + | r | ) |
| 60 | ( | 1 | + | r | ) | = | 155 | − | 100 |
| 60 | × | 1 | + | 60 | r | = | 155 | − | 100 |
| 60 | + | 60 | r | = | 155 | − | 100 |
| 60 | + | 60 | r | = | 55 |
| 60 | r | = | 55 | − | 60 |
| 60 | r | = | - | 5 |
| r | = | - | 5 | ÷ | 60 |
| = | - | 5 | × | 1 60 |
| = | - | 1 | × | 1 12 |
| r | = | - | 1 12 |
| r | = | - 0.083333 |