| 1000 | ( | 1 | + | 3 | x | ) | × | 3 5 | ( | 1 | − | x | ) | = | 7020 |
| Left side of the equation = | 600 | ( | 1 | + | 3 | x | ) | ( | 1 | − | x | ) |
| 600 | ( | 1 | + | 3 | x | ) | ( | 1 | − | x | ) | = | 7020 |
| Left side of the equation = | 600 | × | 1 | ( | 1 | − | x | ) | + | 600 | × | 3 | x | ( | 1 | − | x | ) |
| = | 600 | ( | 1 | − | x | ) | + | 1800 | x | ( | 1 | − | x | ) |
| = | 600 | × | 1 | − | 600 | x | + | 1800 | x | ( | 1 | − | x | ) |
| = | 600 | − | 600 | x | + | 1800 | x | ( | 1 | − | x | ) |
| = | 600 | − | 600 | x | + | 1800 | x | × | 1 | − | 1800 | x | x |
| = | 600 | − | 600 | x | + | 1800 | x | − | 1800 | x | x |
| = | 600 | + | 1200 | x | − | 1800 | x | x |
| 600 | + | 1200 | x | − | 1800 | x | x | = | 7020 |