The answer is B. You first have to solve for x. First you subtract 9 from both sides and get
6x= 3. Then divide both sides by 6 and you’ll get x= 1/2. In each answer you substitute 1/2 for x. You’ll see that in B, 2x+3= 4, if you substitute in 1/2, you get 2(1/2)+3= 4, which equals 1+3=4, which is true.