| ( | 28 | + | x | ) | ÷ | ( | 71 | + | x | ) | = | 7 10 |
| Multiply both sides of the equation by: | ( | 71 | + | x | ) |
| ( | 28 | + | x | ) | = | 7 10 | ( | 71 | + | x | ) |
| 28 | + | x | = | 7 10 | ( | 71 | + | x | ) |
| 28 | + | x | = | 7 10 | × | 71 | + | 7 10 | x |
| 28 | + | x | = | 497 10 | + | 7 10 | x |
| x | − | 7 10 | x | = | 497 10 | − | 28 |
3 10 | x | = | 497 10 | − | 28 |
3 10 | x | = | 217 10 |
| x | = | 217 10 | ÷ | 3 10 |
| = | 217 10 | × | 10 3 |
| = | 217 | × | 1 3 |
| x | = | 217 3 |
| x | = | 72.333333 |