| ( | 180 | − | m | ) | + | ( | 90 | − | m | ) | = | 360 | × | 3 | ÷ | 2 |
| Left side of the equation = | 180 | − | m | + | ( | 90 | − | m | ) |
| = | 180 | − | m | + | 90 | − | m |
| = | 270 | − | 2 | m |
| 270 | − | 2 | m | = | 360 | × | 3 | ÷ | 2 |
| Right side of the equation = | 540 |
| 270 | − | 2 | m | = | 540 |
| - | 2 | m | = | 540 | − | 270 |
| - | 2 | m | = | 270 |
| - | 270 | = | 2 | m |
| 2 | m | = | - | 270 |
| m | = | - | 270 | ÷ | 2 |
| = | - | 270 | × | 1 2 |
| = | - | 135 | × | 1 |
| m | = | - | 135 |