I'm confused: direct, inverse variation equation

The problem states:

Suppose X varies directly with Y and Z, and inversely with W. Suppose also that X = 3 when Y = 2, Z = 6, and W = 16.

Find X when Y = 7, Z = 20, and W = 5.

Please help. Thank you!

Variation exercises translate as follows:

. . . . ."y varies directly as x": y = kx
. . . . ."y varies inversely as x": y = k/x
. . . . ."y varies jointly as x and z": y = kxz

Translate your example into the appropriate form. Plug in the first (complete) set of values and solve for the variation constant "k". Then plug in the second (incomplete) set of values, along with the value of "k", and simplify to find your answer.

If you get stuck, please reply showing how far you have gotten. Thank you.

Eliz.