| ( | 10 | − | t | ) | ( | 980 | − | 8 | t | ) | = | 4000 |
| Left side of the equation = | 10 | ( | 980 | − | 8 | t | ) | − | t | ( | 980 | − | 8 | t | ) |
| = | 10 | × | 980 | − | 10 | × | 8 | t | − | t | ( | 980 | − | 8 | t | ) |
| = | 9800 | − | 80 | t | − | t | ( | 980 | − | 8 | t | ) |
| = | 9800 | − | 80 | t | − | t | × | 980 | + | t | × | 8 | t |
| = | 9800 | − | 1060 | t | + | t | × | 8 | t |
| 9800 | − | 1060 | t | + | t | × | 8 | t | = | 4000 |