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whpalmer4 · Answer

If y varies directly with x, it means there is a relationship $y = kx$ where k is some constant.  If y varies indirectly with z, it means there is a relationship $y = k/z$ where k is some constant.  You've got both, so what does that mean?  Write the equation, and use the known values to solve for k.  Then use the equation with the value of k to find y when x = 21 and z = 7.

anonymous · Answer

what is the equation? @whpalmer4

whpalmer4 · Answer

You have 4 building blocks, k, x, y and z  

you need to arrange them so y = some combination of the other 3.  I've already told you that x has to be in the numerator, and z in the denominator.  k can be anywhere you like :-)

anonymous · Answer

so would it be 2, or 5/3? @whpalmer4

whpalmer4 · Answer

I don't know, I haven't done it yet.  Show me your work, and I'll tell you if you did it correctly.

whpalmer4 · Answer

First, what do you get for the form of the equation?  y = ?