| ( | 30 | − | a | ) | ( | 100 | + | 2 | a | ) | + | ( | 50 | − | a | ) | ( | 50 | + | 2 | a | ) | = | 5300 |
| Left side of the equation = | 30 | ( | 100 | + | 2 | a | ) | − | a | ( | 100 | + | 2 | a | ) | + | ( | 50 | − | a | ) | ( | 50 | + | 2 | a | ) |
| = | 30 | × | 100 | + | 30 | × | 2 | a | − | a | ( | 100 | + | 2 | a | ) | + | ( | 50 | − | a | ) | ( | 50 | + | 2 | a | ) |
| = | 3000 | + | 60 | a | − | a | ( | 100 | + | 2 | a | ) | + | ( | 50 | − | a | ) | ( | 50 | + | 2 | a | ) |
| = | 3000 | + | 60 | a | − | a | × | 100 | − | a | × | 2 | a | + | ( | 50 | − | a | ) | ( | 50 | + | 2 | a | ) |
| = | 3000 | − | 40 | a | − | a | × | 2 | a | + | ( | 50 | − | a | ) | ( | 50 | + | 2 | a | ) |
| = | 3000 | − | 40 | a | − | a | × | 2 | a | + | 50 | ( | 50 | + | 2 | a | ) | − | a | ( | 50 | + | 2 | a | ) |
| = | 3000 | − | 40 | a | − | a | × | 2 | a | + | 50 | × | 50 | + | 50 | × | 2 | a | − | a |
| = | 3000 | − | 40 | a | − | a | × | 2 | a | + | 2500 | + | 100 | a | − | a | ( | 50 | + | 2 | a | ) |
| = | 5500 | + | 60 | a | − | a | × | 2 | a | − | a | ( | 50 | + | 2 | a | ) |
| = | 5500 | + | 60 | a | − | a | × | 2 | a | − | a | × | 50 | − | a | × | 2 | a |
| = | 5500 | + | 10 | a | − | a | × | 2 | a | − | a | × | 2 | a |
| 5500 | + | 10 | a | − | a | × | 2 | a | − | a | × | 2 | a | = | 5300 |