| 7 | × | 13 20 | + | X | × | 1 5 | = | 7 20 | ( | X | + | 7 | ) |
| Left side of the equation = | 91 20 | + | X | × | 1 5 |
91 20 | + | 1 5 | X | = | 7 20 | ( | X | + | 7 | ) |
| Right side of the equation = | 7 20 | X | + | 7 20 | × | 7 |
| = | 7 20 | X | + | 49 20 |
91 20 | + | 1 5 | X | = | 7 20 | X | + | 49 20 |
1 5 | X | − | 7 20 | X | = | 49 20 | − | 91 20 |
| - | 3 20 | X | = | 49 20 | − | 91 20 |
| - | 3 20 | X | = | - | 21 10 |
21 10 | = | 3 20 | X |
3 20 | X | = | 21 10 |
| X | = | 21 10 | ÷ | 3 20 |
| = | 21 10 | × | 20 3 |
| = | 7 | × | 2 |
| X | = | 14 |