If at the election the question of increasing the membership of the board shall be adopted, the membership of the board shall be increased accordingly as of the organization meeting next following the next annual school election and the additional members shall be elected at such annual school election, for terms as follows:
a. If the increase is from three to five, two for three years and one for two years;
b. If the increase is from three to seven, two for three years, one for two years and one for one year;
c. If the increase is from five to seven, one for three years and one for a term of either one or two years, whichever is necessary to cause the terms of two members to expire at each of the next two annual school elections;
d. If the increase is from any other number to nine, for such terms not over three years, as will as soon as possible constitute a board of nine, with three-year terms expiring, three each year.
Each year thereafter successors to the members whose terms expire shall be elected for three years.