(a) Out of ten families, six families have dogs, four have cats and two have neither cats nor dogs. Find the number of families that have both cats…

(a) Out of ten families, six families have dogs, four have cats and two have neither cats nor dogs. Find the number of families that have both cats and dogs?

(b) Using mathematical induction, show that 3ⁿ - 1 is a multiple of 2 for n >= 1.