so if somthing varies inversely then when one value goes up, the other value goes down so xy=z and z has to be the same so lets say that z=16 when x=2 y=8 when x=4 y=4 when x=8 y=2 when x=16 y=1 so xy=z subtitute (3)(5)=15 so if x=5 y=3 x=1 y=15 x=15 y=1