In a survey of B.Com (P) students, 45 students opted for Mathematics, 50 opted for Economics, and 30 opted for both. How many B.Com (P) students have opted for both Mathematics and Economics?

In a Venn diagram problem where the total number of people liking Juice is given by the equation 3y + 12 = 78, find the value of y.

In a detailed survey of a colony regarding beverage preferences, the total number of people who like exactly one beverage is 168 and the number of people who like all the beverages together is 22. Find the difference between the number of people who like exactly one beverage and the people who like all the beverages together.