| ( | x | + | 30 | ) | ÷ | ( | 200 | + | x | ) | = | 3 10 |
| Multiply both sides of the equation by: | ( | 200 | + | x | ) |
| ( | x | + | 30 | ) | = | 3 10 | ( | 200 | + | x | ) |
| x | + | 30 | = | 3 10 | ( | 200 | + | x | ) |
| x | + | 30 | = | 3 10 | × | 200 | + | 3 10 | x |
| x | + | 30 | = | 60 | + | 3 10 | x |
| x | − | 3 10 | x | = | 60 | − | 30 |
7 10 | x | = | 60 | − | 30 |
7 10 | x | = | 30 |
| x | = | 30 | ÷ | 7 10 |
| = | 30 | × | 10 7 |
| x | = | 300 7 |
| x | = | 42.857143 |