In 1998
Let number of students in x = 3k
Number of students in y = 5k and
Number of students in z = 6k
Next year,
number of students in x = 3k + 20% of 3k = 18k/5
Number of students in y = 5k + 10% of 5k = 11k/2
Number of students in z = 6k + 20% of 6k = 36k/5
According to the question,
(18k/5) / (36k/5) = 1/2
Thus, data is insufficient.