| ( | 40 | − | 30 | + | m | − | 40 | ) | ( | 40 | − | m | + | 40 | ) | = | 525 |
| Left side of the equation = | 40 | ( | 40 | − | m | + | 40 | ) | − | 30 | ( | 40 | − | m | + | 40 | ) | + | m | ( | 40 | − | m | + | 40 | ) | − | 40 | ( | 40 | − | m | + | 40 | ) |
| = | 40 | × | 40 | − | 40 | m | + | 40 | × | 40 | − | 30 | ( | 40 | − | m | + | 40 | ) | + | m | ( | 40 | − | m | + | 40 | ) | − | 40 | ( | 40 | − | m | + | 40 | ) |
| = | 1600 | − | 40 | m | + | 1600 | − | 30 | ( | 40 | − | m | + | 40 | ) | + | m | ( | 40 | − | m | + | 40 | ) | − | 40 | ( | 40 | − | m | + | 40 | ) |
| = | 3200 | − | 40 | m | − | 30 | ( | 40 | − | m | + | 40 | ) | + | m | ( | 40 | − | m | + | 40 | ) | − | 40 | ( | 40 | − | m | + | 40 | ) |
| = | 3200 | − | 40 | m | − | 30 | × | 40 | + | 30 | m | − | 30 | × | 40 | + | m | ( | 40 | − | m | + | 40 | ) | − | 40 |
| = | 3200 | − | 40 | m | − | 1200 | + | 30 | m | − | 1200 | + | m | ( | 40 | − | m | + | 40 | ) | − | 40 | ( | 40 | − | m | + | 40 | ) |
| = | 800 | − | 10 | m | + | m | ( | 40 | − | m | + | 40 | ) | − | 40 | ( | 40 | − | m | + | 40 | ) |
| = | 800 | − | 10 | m | + | m | × | 40 | − | m | m | + | m | × | 40 | − | 40 | ( | 40 | − | m | + | 40 | ) |
| = | 800 | + | 70 | m | − | m | m | − | 40 | ( | 40 | − | m | + | 40 | ) |
| = | 800 | + | 70 | m | − | m | m | − | 40 | × | 40 | + | 40 | m | − | 40 | × | 40 |
| = | 800 | + | 70 | m | − | m | m | − | 1600 | + | 40 | m | − | 1600 |
| = | - | 2400 | + | 110 | m | − | m | m |
| - | 2400 | + | 110 | m | − | m | m | = | 525 |