3 2 | ( | 20 | − | a | ) | + | 6 5 | ( | 30 | + | 3 2 | a | ) | = | 69 |
方程左边 = | 3 2 | × | 20 | − | 3 2 | a | + | 6 5 | ( | 30 | + | 3 2 | a | ) |
= | 30 | − | 3 2 | a | + | 6 5 | ( | 30 | + | 3 2 | a | ) |
= | 30 | − | 3 2 | a | + | 6 5 | × | 30 | + | 6 5 | × | 3 2 | a |
= | 30 | − | 3 2 | a | + | 36 | + | 9 5 | a |
= | 66 | + | 3 10 | a |
66 | + | 3 10 | a | = | 69 |
3 10 | a | = | 69 | − | 66 |
3 10 | a | = | 3 |
a | = | 3 | ÷ | 3 10 |
= | 3 | × | 10 3 |
= | 1 | × | 10 |
a | = | 10 |