| ( | 15 | − | 2 | a | − | 8 | ) | ( | 270 | + | 60 | a | ) | = | 1650 |
| 方程左边 = | 15 | ( | 270 | + | 60 | a | ) | − | 2 | a | ( | 270 | + | 60 | a | ) | − | 8 | ( | 270 | + | 60 | a | ) |
| = | 15 | × | 270 | + | 15 | × | 60 | a | − | 2 | a | ( | 270 | + | 60 | a | ) | − | 8 | ( | 270 | + | 60 | a | ) |
| = | 4050 | + | 900 | a | − | 2 | a | ( | 270 | + | 60 | a | ) | − | 8 | ( | 270 | + | 60 | a | ) |
| = | 4050 | + | 900 | a | − | 2 | a | × | 270 | − | 2 | a | × | 60 | a | − | 8 | ( | 270 | + | 60 | a | ) |
| = | 4050 | + | 900 | a | − | 540 | a | − | 120 | a | a | − | 8 | ( | 270 | + | 60 | a | ) |
| = | 4050 | + | 360 | a | − | 120 | a | a | − | 8 | ( | 270 | + | 60 | a | ) |
| = | 4050 | + | 360 | a | − | 120 | a | a | − | 8 | × | 270 | − | 8 | × | 60 | a |
| = | 4050 | + | 360 | a | − | 120 | a | a | − | 2160 | − | 480 | a |
| = | 1890 | − | 120 | a | − | 120 | a | a |
| 1890 | − | 120 | a | − | 120 | a | a | = | 1650 |