| ( | 170 | + | a | − | 20 | ) | ( | 60 | − | 1 10 | a | ) | = | 10080 |
| 方程左边 = | 170 | ( | 60 | − | 1 10 | a | ) | + | a | ( | 60 | − | 1 10 | a | ) | − | 20 | ( | 60 | − | 1 10 | a | ) |
| = | 170 | × | 60 | − | 170 | × | 1 10 | a | + | a | ( | 60 | − | 1 10 | a | ) | − | 20 | ( | 60 | − | 1 10 | a | ) |
| = | 10200 | − | 17 | a | + | a | ( | 60 | − | 1 10 | a | ) | − | 20 | ( | 60 | − | 1 10 | a | ) |
| = | 10200 | − | 17 | a | + | a | × | 60 | − | a | × | 1 10 | a | − | 20 | ( | 60 | − | 1 10 | a | ) |
| = | 10200 | + | 43 | a | − | a | × | 1 10 | a | − | 20 | ( | 60 | − | 1 10 | a | ) |
| = | 10200 | + | 43 | a | − | a | × | 1 10 | a | − | 20 | × | 60 | + | 20 | × | 1 10 | a |
| = | 10200 | + | 43 | a | − | a | × | 1 10 | a | − | 1200 | + | 2 | a |
| = | 9000 | + | 45 | a | − | a | × | 1 10 | a |
| 9000 | + | 45 | a | − | a | × | 1 10 | a | = | 10080 |