| 1 | ( | 40 | − | t | ) | = | 1 | ( | t | − | 30 | ) |
| Left side of the equation = | 1 | × | 40 | − | 1 | t |
| = | 40 | − | 1 | t |
| 40 | − | 1 | t | = | 1 | ( | t | − | 30 | ) |
| Right side of the equation = | 1 | t | − | 1 | × | 30 |
| = | 1 | t | − | 30 |
| 40 | − | 1 | t | = | 1 | t | − | 30 |
| - | 1 | t | − | 1 | t | = | - | 30 | − | 40 |
| - | 2 | t | = | - | 30 | − | 40 |
| - | 2 | t | = | - | 70 |
| 70 | = | 2 | t |
| 2 | t | = | 70 |
| t | = | 70 | ÷ | 2 |
| = | 70 | × | 1 2 |
| = | 35 | × | 1 |
| t | = | 35 |