| ( | 300 | + | x | ) | ( | 120 | + | x | ) | = | 24 | ÷ | 15 |
| Left side of the equation = | 300 | ( | 120 | + | x | ) | + | x | ( | 120 | + | x | ) |
| = | 300 | × | 120 | + | 300 | x | + | x | ( | 120 | + | x | ) |
| = | 36000 | + | 300 | x | + | x | ( | 120 | + | x | ) |
| = | 36000 | + | 300 | x | + | x | × | 120 | + | x | x |
| = | 36000 | + | 420 | x | + | x | x |
| 36000 | + | 420 | x | + | x | x | = | 24 | ÷ | 15 |
| Right side of the equation = | 8 5 |
| 36000 | + | 420 | x | + | x | x | = | 8 5 |