we are given
y varies directly with x
so, we can write equation as
where
k is a constant
now, we need to find k
we are given
y=3 when x=8
so, we can plug it and find k
now, we can plug it back
(A)
we have got equation as
for finding inverse , we can switch x and y
now, we can solve for y
............Answer
(B)
we have
we can plug x=4 and find y
................Answer