| ( | 70 | + | 2 | x | ) | ( | 40 | + | 2 | x | ) | = | 4800 |
| Left side of the equation = | 70 | ( | 40 | + | 2 | x | ) | + | 2 | x | ( | 40 | + | 2 | x | ) |
| = | 70 | × | 40 | + | 70 | × | 2 | x | + | 2 | x | ( | 40 | + | 2 | x | ) |
| = | 2800 | + | 140 | x | + | 2 | x | ( | 40 | + | 2 | x | ) |
| = | 2800 | + | 140 | x | + | 2 | x | × | 40 | + | 2 | x | × | 2 | x |
| = | 2800 | + | 140 | x | + | 80 | x | + | 4 | x | x |
| = | 2800 | + | 220 | x | + | 4 | x | x |
| 2800 | + | 220 | x | + | 4 | x | x | = | 4800 |