| ( | 15 | − | X | ) | ( | 400 | + | 5 | X | ) | = | 4620 |
| Left side of the equation = | 15 | ( | 400 | + | 5 | X | ) | − | X | ( | 400 | + | 5 | X | ) |
| = | 15 | × | 400 | + | 15 | × | 5 | X | − | X | ( | 400 | + | 5 | X | ) |
| = | 6000 | + | 75 | X | − | X | ( | 400 | + | 5 | X | ) |
| = | 6000 | + | 75 | X | − | X | × | 400 | − | X | × | 5 | X |
| = | 6000 | − | 325 | X | − | X | × | 5 | X |
| 6000 | − | 325 | X | − | X | × | 5 | X | = | 4620 |