| ( | 287 5 | × | 100 | + | 0 | ) | ÷ | ( | 100 | + | x | ) | = | 13 |
| Multiply both sides of the equation by: | ( | 100 | + | x | ) |
| ( | 287 5 | × | 100 | + | 0 | ) | = | 13 | ( | 100 | + | x | ) |
287 5 | × | 100 | + | 0 | = | 13 | ( | 100 | + | x | ) |
287 5 | × | 100 | + | 0 | = | 13 | × | 100 | + | 13 | x |
| 5740 | + | 0 | = | 1300 | + | 13 | x |
| 5740 | = | 1300 | + | 13 | x |
| - | 13 | x | = | 1300 | − | 5740 |
| - | 13 | x | = | - | 4440 |
| 4440 | = | 13 | x |
| 13 | x | = | 4440 |
| x | = | 4440 | ÷ | 13 |
| = | 4440 | × | 1 13 |
| x | = | 4440 13 |
| x | = | 341.538462 |