Suppose that y varies directly with x and inversely with z and y = 28 when x = 32 and z = 8. write the quation that models the relationship. then find when x = 12 and z = 3

Given that y varies directly with x and inversely with z, then:
a] Equation that models the relationship
y=kx/z
where k is the constant of proportionality, given by:
k=yz/x
k=(28×8)/32
k=7
The equation that models the relationship is:
y=7x/z

b] 
find y when x = 12 and z = 3
The value of y will be given:
y=(7×12)/3
y=28