| ( | 38 | − | a | ) | ( | 200 | + | 2 | a | ) | = | 1150 |
| Left side of the equation = | 38 | ( | 200 | + | 2 | a | ) | − | a | ( | 200 | + | 2 | a | ) |
| = | 38 | × | 200 | + | 38 | × | 2 | a | − | a | ( | 200 | + | 2 | a | ) |
| = | 7600 | + | 76 | a | − | a | ( | 200 | + | 2 | a | ) |
| = | 7600 | + | 76 | a | − | a | × | 200 | − | a | × | 2 | a |
| = | 7600 | − | 124 | a | − | a | × | 2 | a |
| 7600 | − | 124 | a | − | a | × | 2 | a | = | 1150 |