Let x = month rent this years;

    y =   that  of last year.


Then from condition, you have these equations

    x = 3y - 32000    (1)

    x = y  + 4000     (2)


The rest is just routine exercise.


For example, from the equations you immediately get


    3y - 32000 = y + 4000,


and then


    2y = 32000 + 4000 = 36000

     y                = 36000/2 = 18000


and so on . . .