8 5 | X | + | 16 | + | 20 | + | 12 5 | ( | 40 | − | X | − | 20 | ) | + | 2 | = | 398 5 |
| Left side of the equation = | 8 5 | X | + | 38 | + | 12 5 | ( | 40 | − | X | − | 20 | ) |
8 5 | X | + | 38 | + | 12 5 | ( | 40 | − | X | − | 20 | ) | = | 398 5 |
| Left side of the equation = | 8 5 | X | + | 38 | + | 12 5 | × | 40 | − | 12 5 | X | − | 12 5 | × | 20 |
| = | 8 5 | X | + | 38 | + | 96 | − | 12 5 | X | − | 48 |
| = | - | 4 5 | X | + | 86 |
| - | 4 5 | X | + | 86 | = | 398 5 |
| - | 4 5 | X | = | 398 5 | − | 86 |
| - | 4 5 | X | = | - | 32 5 |
32 5 | = | 4 5 | X |
4 5 | X | = | 32 5 |
| X | = | 32 5 | ÷ | 4 5 |
| = | 32 5 | × | 5 4 |
| = | 8 | × | 1 |
| X | = | 8 |