| X | − | 1 5 | X | − | 1 20 | X | − | 3 | = | 81 | + | 1 5 | × | 81 |
| Left side of the equation = | 3 4 | X | − | 3 |
3 4 | X | − | 3 | = | 81 | + | 1 5 | × | 81 |
| Right side of the equation = | 81 | + | 81 5 |
| = | 486 5 |
3 4 | X | − | 3 | = | 486 5 |
3 4 | X | = | 486 5 | + | 3 |
3 4 | X | = | 501 5 |
| X | = | 501 5 | ÷ | 3 4 |
| = | 501 5 | × | 4 3 |
| = | 167 5 | × | 4 |
| X | = | 668 5 |
| X | = | 133.6 |