| ( | 100 | − | s | ) | ( | 2 | s | + | 40 | ) | = | 100 | ( | s | − | 40 | ) |
| Left side of the equation = | 100 | ( | 2 | s | + | 40 | ) | − | s | ( | 2 | s | + | 40 | ) |
| = | 100 | × | 2 | s | + | 100 | × | 40 | − | s | ( | 2 | s | + | 40 | ) |
| = | 200 | s | + | 4000 | − | s | ( | 2 | s | + | 40 | ) |
| = | 200 | s | + | 4000 | − | s | × | 2 | s | − | s | × | 40 |
| = | 160 | s | + | 4000 | − | s | × | 2 | s |
| 160 | s | + | 4000 | − | s | × | 2 | s | = | 100 | ( | s | − | 40 | ) |
| Right side of the equation = | 100 | s | − | 100 | × | 40 |
| = | 100 | s | − | 4000 |
| 160 | s | + | 4000 | − | s | × | 2 | s | = | 100 | s | − | 4000 |