we know that
A relationship between two variables, x, and y, represent an inverse variation if it can be expressed in the form y*x=k or y=k/x
Let
b--------> the number of birds
d--------> the number of dogs
in this problem we have
b*d=k
where
k is a constant
when
d=40 dogs b=10 birds
40*10=400
d=50 dogs b=8 birds
50*8=400
the value of k=400
the equation is
b=k/d-----------------> b=400/d
for d=10 dogs
Find the value of b
b=400/d------- b=400/10-------> b=40 birds
therefore
the answer is
40 birds