fifty family were interviewed regarding 2 known brands of soaps they prefer to use labeled a, a and b 

15 families were using brand a
20 families were using brand b 
7 families were both a and b

usse venn diagram

1.how many families were using brand a only? 
2.how many families were using brand b only?
3.how many families were using atlest two brands of soaps ?
4.how many families do not use any of the two brands of soap?