Two-thirds of the 96 members approved of the plan what percent of the members did not approve of the plan

If 2/3 of the 96 members did not approve, then 1/3 of the members must have approved. 
If you want to find 1/3's percentage equivalent, you would never see the end of it- literally. The actual percentage is 33.3% with a repeater bar over the 0.3, meaning that the 3's go on forever. 
Therefore, if your teacher wants you to round to the nearest tenth or hundredth, your answer would be 33.3% or 33.33%, respectively. Just 33% is sometimes accepted as well.
Hope that helped you!