The answer is .30
Since 30 students responded high interest so the relative frequency of students with high interest is
30/100=0.30
So required relative frequency is 30%.
Total frequencies: 3+7+11+22+40+24+9+4=120
The total frequencies of those who sales 1600 or more is 24+9+4=37
So required relative frequency will be
37/120 = 0.308