Mary fed Luna 1+1=2 cups of kibble.
Frank fed Luna 1-cup plus twice 1-cup, or 1+2=3 cups of kibble.
In total, they fed Luna 2+3=<<2+3=5>>5 cups of kibble.
Thus, if the new bag held 12 cups of kibble, the next morning, 12-5=<<12-5=7>>7 cups of kibble remained in the bag.
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