| 3 | ( | 80 | − | t | ) | = | 21 | ( | t | − | 56 | ) |
| Left side of the equation = | 3 | × | 80 | − | 3 | t |
| = | 240 | − | 3 | t |
| 240 | − | 3 | t | = | 21 | ( | t | − | 56 | ) |
| Right side of the equation = | 21 | t | − | 21 | × | 56 |
| = | 21 | t | − | 1176 |
| 240 | − | 3 | t | = | 21 | t | − | 1176 |
| - | 3 | t | − | 21 | t | = | - | 1176 | − | 240 |
| - | 24 | t | = | - | 1176 | − | 240 |
| - | 24 | t | = | - | 1416 |
| 1416 | = | 24 | t |
| 24 | t | = | 1416 |
| t | = | 1416 | ÷ | 24 |
| = | 1416 | × | 1 24 |
| = | 59 | × | 1 |
| t | = | 59 |