| ( | 400 | − | X | ) | ( | 8 | + | 1 10 | X | ) | = | 5600 |
| Left side of the equation = | 400 | ( | 8 | + | 1 10 | X | ) | − | X | ( | 8 | + | 1 10 | X | ) |
| = | 400 | × | 8 | + | 400 | × | 1 10 | X | − | X | ( | 8 | + | 1 10 | X | ) |
| = | 3200 | + | 40 | X | − | X | ( | 8 | + | 1 10 | X | ) |
| = | 3200 | + | 40 | X | − | X | × | 8 | − | X | × | 1 10 | X |
| = | 3200 | + | 32 | X | − | X | × | 1 10 | X |
| 3200 | + | 32 | X | − | X | × | 1 10 | X | = | 5600 |