What number when added to 5.2 equals 12.6?

Acertain volume of water contains 100000 hydrogen atoms and 50,000 oxygen atoms how many hydrogen atoms are in a volume of water containing 4 million oxygen atoms

Aschool had an election where the candidates received votes in the ratio 1: 2: 3. if the winning candidate received 210 votes, how many total people voted in the election?

Xy x xy if a and b are positive integers such that a*b=9 and b*a=72 what is the value of a/b