Upon the ballots used at all elections provided for in section 284 of this Constitution the substance or subject matter of each proposed amendment shall be so printed that the nature thereof shall be clearly indicated. Follow- ing each proposed amendment on the ballot shall be printed the word ‘‘Yes’’ and immediately under that shall be printed the word ‘‘No.’’ The choice of the elector shall be indicated by a cross mark made by him or under his direction, opposite the word expressing his desire, and no amendment shall be adopted unless it receives the affirmative vote of a majority of all the qualified electors who vote at such election.