If there are 3/4 apples as oranges and 5 times oranges as bananas.What is the ratio of apples to bananas ?

I solve this question by : apples= 3/4 oranges and oranges =5 bananas.
So, 4 apples = 3 oranges
to equate the value of oranges so we be able to compare, I multiplied the oranges by 3. So we have, 3 oranges = 15 bananas
So, we have 4 apples to 15 banana

The correct answer is 15 to 4 not 4 to 15 … What is the thing that I am missing ?

I think you went wrong in the first expression, its A/O=3/4 so 3 Apples for 4 oranges and O/B=5/1
so now we want to equal the orange ratio for both ratio, so we multiply first ratio by 5 and second one by 4, we get A/O= 15/20 and O/B= 20/4 so A/B= 15/4