[" 21.Present age of father is "42" years and that of his son is "14" years."],[" Find the ratio of "],[" (a) Present age of father to the present age of son."],[" (b) Age of the father to the age of son,when son was "12" years old."],[" (c) Age of father after "10" years to the age of son after "10" years."],[" (d) Age of father to the age of son when father was "30" years old."]