Answer:
27
Explanation:
Let the first quantity be y
Let the second quantity be x
Since the two quantities vary inversely, therefore, the first, y varies inversely to the second, x:

∴
.................................. (1)
where k is the constant of proportionality.
When the first, y = 15, the value of the second, x = 18
∴ From eqn (1), we have to find k

k = 15 x 18 = 270
Now, the value of the second quantity x, when the first y = 10 is

Making x subject of formular, we have

The value of the second quantity is 27