Answer:
Combined equation is
Step-by-step explanation:
a varies directly as b and inversely as c.
This can be written as
a =
a = kb
where k is the proportionality constant
-------------------------------------(1)
Now lets find the k value bu substituting the given a, b,c values
36 = 12 k
k = 3
Thus the eq(1) becomes
Let us now find the value of a when b=7 and c = 3
a = 7