we have that
n(U)=100
so
(q+r+10+6)+(r+v)+w+x=100 ------> equation 1
n(A)=50
so
(q+r+10+6)=50 -------> equation 2
n(B)=40
so
(10+6+v+s)=40 -------> equation 3
n(C)=30
so
(r+6+v+w)=30 -------> equation 4


so
(6+v)=14 -------> v=14-6 --------> v=8

so
r+6=13 --------> r=13-6 -------> r=7
step 1
substitute equation 2 in equation 1
50+(r+v)+w+x=100 ------> equation 5
we have
(10+6+v+s)=40 -------> equation 3
(r+6+v+w)=30 -------> equation 4
50+(r+v)+w+x=100 ------> equation 5
substitute the values of v and r in equation 4,5 and 6
(10+6+8+s)=40 --------> s=40-24 -------> s=16
equation 4
(7+6+8+w)=30 -------> W=30-21 -------> W=9
equation 5
50+(7+8)+9+x=100 -------> x=100-74 ------->x=26