Question

What is the ratio of the number of letter A to the number of letter B to the
number of letter N in the word "BANANA"?

Answer 1

in 'BANANA'   A appears 3 times and B 1 times and N 2 times 
number of A / number of B = 3/1 = 3:1
number of A / number of N = 3/2 = 3:2

Answer 2

Ratio required A:B:N
In the word BANANA,A appears 3 times,B only 1 time and N 2 times.
Therefore the required ratio is 3:2:1.