Answer: There are 20 girls who preferred insta.
Step-by-step explanation:
Since we have given that
Total number of students who were surveyed = 100
Number of boys who preferred insta among 50 boys = 40
Number of girls who preferred snpchat among 50 girls = 30
We need to find the number of girls who preferred insta.
So, Number of girls who preferred insta = Total number of girls - Number of girls who preferred snpchat.

Hence, there are 20 girls who preferred insta.