| 4 | ( | m | + | 200 | ) | = | 5 | ( | m | − | 280 | ) |
| Left side of the equation = | 4 | m | + | 4 | × | 200 |
| = | 4 | m | + | 800 |
| 4 | m | + | 800 | = | 5 | ( | m | − | 280 | ) |
| Right side of the equation = | 5 | m | − | 5 | × | 280 |
| = | 5 | m | − | 1400 |
| 4 | m | + | 800 | = | 5 | m | − | 1400 |
| 4 | m | − | 5 | m | = | - | 1400 | − | 800 |
| - | m | = | - | 1400 | − | 800 |
| - | m | = | - | 1400 | − | 800 |
| - | m | = | - | 2200 |
| 2200 | = | m |
| m | = | 2200 |