The number of pair of positive integers whose sum is 99 and HCF is 9 is

I am not sure, may be 5 is correct

Let the numbers be 9x and
9y where x and y are prime to
each other.
According to the question,
9x + 9y = 99
9(x + y) = 99
x + y = 11
Possible pairs = (1, 10) (2, 9), (3, 8),
(4, 7), (5, 6)