| ( | 4 | X | + | 50 | ) | ( | 20 | − | 5 | X | ) | = | 0 |
| Left side of the equation = | 4 | X | ( | 20 | − | 5 | X | ) | + | 50 | ( | 20 | − | 5 | X | ) |
| = | 4 | X | × | 20 | − | 4 | X | × | 5 | X | + | 50 | ( | 20 | − | 5 | X | ) |
| = | 80 | X | − | 20 | X | X | + | 50 | ( | 20 | − | 5 | X | ) |
| = | 80 | X | − | 20 | X | X | + | 50 | × | 20 | − | 50 | × | 5 | X |
| = | 80 | X | − | 20 | X | X | + | 1000 | − | 250 | X |
| = | - | 170 | X | − | 20 | X | X | + | 1000 |
| - | 170 | X | − | 20 | X | X | + | 1000 | = | 0 |
| X1= | - | 25 2 |
| X2=4 |