Sets

In a group of 15 people, 7 read French, 8 read English while 3 of them read none of them. How many read French and English both?
Find the number of subsets of a set whose set contains $$6$$ elements.
If $$A=\left\{ 1,\cfrac { 1 }{ 4 } ,\cfrac { 1 }{ 9 } ,\cfrac { 1 }{ 16 } ,\cfrac { 1 }{ 25 }  \right\} $$, then write $$A$$ in Set-builder form.
Let  $$A , B$$  be two set such that  $$n ( A ) = 4$$  and  $$n ( B ) = 6$$  then the least possible number of elements in the power set  of  $$( A \cup B )$$  is
Write two sets each involving algebraic and geometrical ideas .