What is the value of x/yz ?
(1) x = y/2 and z = 2x/5 .
(2) x/z = 2/5 and 1/y= 1/10
X/yz can be simplified as (x/z) * (1/y)
From statement 1, we get x / y = 1/2 and 1/2 = 5/2x. This answer will vary for every value of x, hence A is not sufficient.
From statement 2, we have x/z= 2/5 and 1/y = 1/10, so multiplying both of them (2/5) * (1/ 10) = 1/25
Hence B is the answer.