| ( | 1 | − | m | + | 3 | ) | ( | m | + | 4 | ) | = | 7 |
| Left side of the equation = | 1 | ( | m | + | 4 | ) | − | m | ( | m | + | 4 | ) | + | 3 | ( | m | + | 4 | ) |
| = | 1 | m | + | 1 | × | 4 | − | m | ( | m | + | 4 | ) | + | 3 | ( | m | + | 4 | ) |
| = | 1 | m | + | 4 | − | m | ( | m | + | 4 | ) | + | 3 | ( | m | + | 4 | ) |
| = | 1 | m | + | 4 | − | m | m | − | m | × | 4 | + | 3 | ( | m | + | 4 | ) |
| = | - | 3 | m | + | 4 | − | m | m | + | 3 | ( | m | + | 4 | ) |
| = | - | 3 | m | + | 4 | − | m | m | + | 3 | m | + | 3 | × | 4 |
| = | - | 3 | m | + | 4 | − | m | m | + | 3 | m | + | 12 |
| = | - | 0 | m | + | 16 | − | m | m |
| - | 0 | m | + | 16 | − | m | m | = | 7 |