| 500 | X | × | 9 10 | + | ( | X | − | 500 | ) | X | × | 4 5 | = | 490 |
| Left side of the equation = | 450 | X | + | ( | X | − | 500 | ) | X | × | 4 5 |
| 450 | X | + | ( | X | − | 500 | ) | X | × | 4 5 | = | 490 |
| Left side of the equation = | 450 | X | + | X | X | × | 4 5 | − | 500 | X | × | 4 5 |
| = | 450 | X | + | X | X | × | 4 5 | − | 400 | X |
| = | 50 | X | + | X | X | × | 4 5 |
| 50 | X | + | X | X | × | 4 5 | = | 490 |