OK, your problem statement lacks a figure and clarity, but I'm assuming that the measure of the angle in question is 2x/3 = 2(90°)/3 = 60°. Vertical angles are equal in measure, so the vertical angle to 2x/3 would also be 60°.
Tutors are good, but we can't see figures unless you post them and I had to guess what (2/3)x represented. In the future, be sure to post all of the information given in the problem and any figures that apply.