9:18
why?
to simplify 15:30, we can find a common factor. 15 and 30 are both divisible by 15.
15/15=1
30/15=2
Now, our new ratio 1:2.
we can find what fractions are equivalent. both 120:60 and 40:2 have a first number bigger than the second, so they are obviously eliminated. that leaves us with 9:18. when we simplify by dividing both numbers by 9, we get 1:2. that is your answer. hope this helped