| ( | 20 | + | m | ) | × | 5 | = | ( | 15 | + | m | ) | × | 6 |
| Left side of the equation = | 20 | × | 5 | + | m | × | 5 |
| = | 100 | + | m | × | 5 |
| 100 | + | 5 | m | = | ( | 15 | + | m | ) | × | 6 |
| Right side of the equation = | 15 | × | 6 | + | m | × | 6 |
| = | 90 | + | m | × | 6 |
| 100 | + | 5 | m | = | 90 | + | 6 | m |
| 5 | m | − | 6 | m | = | 90 | − | 100 |
| - | m | = | 90 | − | 100 |
| - | m | = | 90 | − | 100 |
| - | m | = | - | 10 |
| 10 | = | m |
| m | = | 10 |