| 21 | ( | t | − | 56 | ) | = | 7 | ( | 80 | − | t | ) |
| Left side of the equation = | 21 | t | − | 21 | × | 56 |
| = | 21 | t | − | 1176 |
| 21 | t | − | 1176 | = | 7 | ( | 80 | − | t | ) |
| Right side of the equation = | 7 | × | 80 | − | 7 | t |
| = | 560 | − | 7 | t |
| 21 | t | − | 1176 | = | 560 | − | 7 | t |
| 21 | t | + | 7 | t | = | 560 | + | 1176 |
| 28 | t | = | 560 | + | 1176 |
| 28 | t | = | 1736 |
| t | = | 1736 | ÷ | 28 |
| = | 1736 | × | 1 28 |
| = | 62 | × | 1 |
| t | = | 62 |