Notwithstanding any change in the boundaries of a state-aided district or the annexation to, or the inclusion in, another district of a state-aided district, the state-aided district as it existed immediately prior to the effective date of the action shall be continued in existence for the determination of the assessed valuation of the property therein and for the purposes of the computations provided by Sections 15729, 15730, and 15733; and all the computations required to be made pursuant to those sections shall be made exactly as if there had been no change of boundaries, annexations, or inclusion, except as otherwise provided in Sections 15792 and 15793.