| ( | 1 40 | + | x | ) | x | ÷ | ( | 1 40 | − | x | ) | = | 31 5 | ÷ | 100000000 |
| Multiply both sides of the equation by: | ( | 1 40 | − | x | ) |
| ( | 1 40 | + | x | ) | x | = | 31 5 | ÷ | 100000000 | × | ( | 1 40 | − | x | ) |
1 40 | x | + | x | x | = | 31 5 | ÷ | 100000000 | × | ( | 1 40 | − | x | ) |
1 40 | x | + | x | x | = | 31 5 | ÷ | 100000000 | × | 1 40 | − | 31 5 | ÷ | 100000000 | × | x |