| ( | m | − | 15 | ) | ( | - | 10 | m | + | 310 | ) | = | 630 |
| Left side of the equation = | m | ( | - | 10 | m | + | 310 | ) | − | 15 | ( | - | 10 | m | + | 310 | ) |
| = | - | m | × | 10 | m | + | m | × | 310 | − | 15 | ( | - | 10 | m | + | 310 | ) |
| = | - | m | × | 10 | m | + | 310 | m | + | 15 | × | 10 | m | − | 15 | × | 310 |
| = | - | m | × | 10 | m | + | 310 | m | + | 150 | m | − | 4650 |
| = | - | m | × | 10 | m | + | 460 | m | − | 4650 |
| - | m | × | 10 | m | + | 460 | m | − | 4650 | = | 630 |