Answer:
0.75
Explanation:
Total number of people = 400
Number of people who say yes to gun laws being more stringent = 300
Number of people who say no to gun laws being more stringent = 100
The proportion of people who will say yes = Number of people who say yes to gun laws being more stringent / Total number of people

∴ Proportion in the population who will respond "yes" is 0.75