| 180 | − | ( | ( | 40 | − | y | ) | + | 30 | ) | = | 240 | − | ( | y | + | 50 | ) |
| Left side of the equation = | 180 | − | ( | 40 | − | y | ) | − | 30 |
| = | 150 | − | ( | 40 | − | y | ) |
| = | 150 | − | 40 | + | y |
| = | 110 | + | y |
| 110 | + | y | = | 240 | − | ( | y | + | 50 | ) |
| Right side of the equation = | 240 | − | y | − | 50 |
| = | 190 | − | y |
| 110 | + | y | = | 190 | − | y |
| y | + | y | = | 190 | − | 110 |
| 2 | y | = | 190 | − | 110 |
| 2 | y | = | 80 |
| y | = | 80 | ÷ | 2 |
| = | 80 | × | 1 2 |
| = | 40 | × | 1 |
| y | = | 40 |