| ( | 19 | − | m | ) | ( | 300 | + | 30 | m | ) | = | 6300 |
| Left side of the equation = | 19 | ( | 300 | + | 30 | m | ) | − | m | ( | 300 | + | 30 | m | ) |
| = | 19 | × | 300 | + | 19 | × | 30 | m | − | m | ( | 300 | + | 30 | m | ) |
| = | 5700 | + | 570 | m | − | m | ( | 300 | + | 30 | m | ) |
| = | 5700 | + | 570 | m | − | m | × | 300 | − | m | × | 30 | m |
| = | 5700 | + | 270 | m | − | m | × | 30 | m |
| 5700 | + | 270 | m | − | m | × | 30 | m | = | 6300 |