In case any school district has heretofore incurred, or shall hereafter incur, indebtedness for strictly school purposes and has heretofore, or shall hereafter, become merged with another district as provided in *RCW
28A.315.010 through
28A.315.680 and
28A.315.900, the directors of the last named district may, after such merger, cause to be submitted to the voters within the limits of the district which incurred the obligations, the question of validating and ratifying such indebtedness. The vote shall be taken and the question determined in the manner prescribed in RCW
28A.535.020,
28A.535.030, and
28A.535.040. The directors of the district to which the district incurring the obligations was merged shall make provisions for payment of the indebtedness so validated by certifying the amount thereof in the manner prescribed in RCW
28A.535.070: PROVIDED, Such enlarged district may pay a part, or all, of such validating indebtedness from any funds available or by issuing bonds therefor when such enlarged district has taken over property of any district and in making such adjustment and apportionment as provided in *RCW
28A.315.010 through
28A.315.680 and
28A.315.900, the value of the property received shall be found to exceed the total indebtedness of the district annexed to the extent of such value over the total indebtedness of the district annexed.