Answer:
30 : 10
Explanation:
the answer is 30 : 10 because if you multiply 3 : 1 by the same number ( in this case 10) then it is an equivalent ratio.
10 : 9 doesn't work because when you divide 10 by 3 and divide 9 by 1 it is not the same answer so that is not an equivalent ratio. Same goes for 26 : 7
when you divide it by the same number it will no equal 3 : 1.