\(-3 \frac{1}{2}\)
Explanation
First subtract 7a from both sides to get all the a terms on one side. Then 2 = 3a – 5 + 2a – 7a. Combine all the a terms: 2 = –2a – 5. Add 5 to both sides to get 7 = –2a.
Dividing both sides by –2, \(a=-7 / 2=-3 \frac{1}{2}\)