If y varies jointly as x and z and y = 60 when x = 3 and z = 4, find y when x is 6 and z is 8.
can aanyone walk me through how to do this?

 if y varies jointly with x &  z
 then  y  =  kxz         k =  constant  >  you need to find the constant
                                first before you can solve this kind of problem
60  = k3*4        y = 60      when  x is 3 & z is 4
12k = 60
k =  5
Thus  y =      5*6*8      when    x =6  &  z =8
       y  =  240