| ( | 324 | − | m | − | 12 | ) | ( | 300 | + | 50 | m | ) | = | 4000 |
| Left side of the equation = | 324 | ( | 300 | + | 50 | m | ) | − | m | ( | 300 | + | 50 | m | ) | − | 12 | ( | 300 | + | 50 | m | ) |
| = | 324 | × | 300 | + | 324 | × | 50 | m | − | m | ( | 300 | + | 50 | m | ) | − | 12 | ( | 300 | + | 50 | m | ) |
| = | 97200 | + | 16200 | m | − | m | ( | 300 | + | 50 | m | ) | − | 12 | ( | 300 | + | 50 | m | ) |
| = | 97200 | + | 16200 | m | − | m | × | 300 | − | m | × | 50 | m | − | 12 | ( | 300 | + | 50 | m | ) |
| = | 97200 | + | 15900 | m | − | m | × | 50 | m | − | 12 | ( | 300 | + | 50 | m | ) |
| = | 97200 | + | 15900 | m | − | m | × | 50 | m | − | 12 | × | 300 | − | 12 | × | 50 | m |
| = | 97200 | + | 15900 | m | − | m | × | 50 | m | − | 3600 | − | 600 | m |
| = | 93600 | + | 15300 | m | − | m | × | 50 | m |
| 93600 | + | 15300 | m | − | m | × | 50 | m | = | 4000 |