Complex sentence: Davao del Norte (officially renamed to "Davao" in 1972) was represented in the Interim Batasang Pambansa as part of Region XI from 1978 to 1984, and returned three representatives, elected at-large to the Regular Batasang Pambansa in 1984.
Split into simpler sentences: Davao del Norte--officially renamed to "Davao" in 1972--was represented in the Interim Batasang Pambansa as part of Region XI from 1978 to 1984. The province returned three representatives, elected at-large, to the Regular Batasang Pambansa in 1984.