If y varies jointly as x and z. If y = 12 when x = 18 and z = 6, find y when x = 81 and
z = 7.


If y varies inversely as x and y = 5 when x = 5, find y when x = 45.


If y varies directly as z and inversely as x and y = 27 and z = –3 when x = 2, find x when
y = 9 and z = 5.