| 300 | ( | 10 | + | X | ) | = | 350 | ( | 5 | + | X | ) |
| Left side of the equation = | 300 | × | 10 | + | 300 | X |
| = | 3000 | + | 300 | X |
| 3000 | + | 300 | X | = | 350 | ( | 5 | + | X | ) |
| Right side of the equation = | 350 | × | 5 | + | 350 | X |
| = | 1750 | + | 350 | X |
| 3000 | + | 300 | X | = | 1750 | + | 350 | X |
| 300 | X | − | 350 | X | = | 1750 | − | 3000 |
| - | 50 | X | = | 1750 | − | 3000 |
| - | 50 | X | = | - | 1250 |
| 1250 | = | 50 | X |
| 50 | X | = | 1250 |
| X | = | 1250 | ÷ | 50 |
| = | 1250 | × | 1 50 |
| = | 25 | × | 1 |
| X | = | 25 |