joint and combined variation

[ibueno1]

i need help on this problem you are supposed to find an equation of combined variation and then solve for the missing value

w varies directly as x and inversely as y.One set of values is w=3,x=9, and y=2. Find w when x=15 and y=5.

i would really appreciate your help :D :) :D :P 8-)

[skeeter]

w varies directly as x and inversely as y ...

w = kx/y

substitute in your first set of values, solve for the constant of proportionality, k.

now, substitute your second set of values and the value you determined for k to find the unknown variable.