The board having jurisdiction, upon being satisfied that copies of the petition have been posted and notices have been served and posted as required, or that at least seventy percent of the qualified electors who are owners of lands affected have signed the original petition and that notices have been served personally or left at the abode of those who may have failed to sign the original petition, proof of which shall be shown by affidavit, shall proceed to examine the proposed highway and shall hear any reasons for or against the laying out, altering, or discontinuing of the same, and shall decide upon the application as it deems proper.