Answer:
a=2, b=7 (fourth option)
Explanation:
When you subtract the 2x from both sides, you are left with 0 x's. Then when you subtract the 6 from both sides, you are left with -1. So you will have 0= -1, which does not make sense meaning the answer is no solution. When inserting the other options into the equation, they all solve for x. Hope this helps!