In which direction will the parabola open?

Which of the following is most likely the next step in the series? a3z, b6y, c9x, d12w, е15v, f18u

4+(2+x) can you me solve this problem

Jared had 3/7 of the minutes on a family phone plan remaining for the month. the plan is shared by 2 people. if divided equally what portion of the minutes remaining on the phone plan would be avalible for each person