Answer :
We know the number of days that saw rain, n(R) = 10, the number of days that saw high winds, n(W) = 54, and the number of days that saw either rain or high winds, n(R∪W) = 56.
And we need to find the number of days that saw both rain and high winds, n(R∩W).
So, we can use the formula:
[tex]n\mleft(R\cap W\mright)=n(R)+n(W)-n\mleft(R\cup W\mright)[/tex]Thus, we obtain:
[tex]n\mleft(R\cap W\mright)=10+54-56=64-56=8[/tex]Therefore, 8 days saw both rain and high winds.