| ( | 3000 | − | x | ) | ÷ | 290 | = | ( | 3000 | + | x | ) | ÷ | 310 |
| Left side of the equation = | 3000 | × | 1 290 | − | x | × | 1 290 |
| = | 300 29 | − | x | × | 1 290 |
300 29 | − | 1 290 | x | = | ( | 3000 | + | x | ) | ÷ | 310 |
| Right side of the equation = | 3000 | × | 1 310 | + | x | × | 1 310 |
| = | 300 31 | + | x | × | 1 310 |
300 29 | − | 1 290 | x | = | 300 31 | + | 1 310 | x |
| - | 1 290 | x | − | 1 310 | x | = | 300 31 | − | 300 29 |
| - | 6 899 | x | = | 300 31 | − | 300 29 |
| - | 6 899 | x | = | - | 600 899 |
600 899 | = | 6 899 | x |
6 899 | x | = | 600 899 |
| x | = | 600 899 | ÷ | 6 899 |
| = | 600 899 | × | 899 6 |
| = | 100 | × | 1 |
| x | = | 100 |