| ( | 5 | + | x | ) | ( | 460 | − | 40 | x | ) | = | 2720 |
| Left side of the equation = | 5 | ( | 460 | − | 40 | x | ) | + | x | ( | 460 | − | 40 | x | ) |
| = | 5 | × | 460 | − | 5 | × | 40 | x | + | x | ( | 460 | − | 40 | x | ) |
| = | 2300 | − | 200 | x | + | x | ( | 460 | − | 40 | x | ) |
| = | 2300 | − | 200 | x | + | x | × | 460 | − | x | × | 40 | x |
| = | 2300 | + | 260 | x | − | x | × | 40 | x |
| 2300 | + | 260 | x | − | x | × | 40 | x | = | 2720 |
| x2= | 7 2 |