I want to know algo for below problem

you are given 3 values say a, b and x. you can perform 3 ops: X-> a=a+b Y-> a=a-b Z-> b = a-b now performing these ops on a and b you have to get value x in var a. ex: a = 19, b = 7, x = 27 if you perform YZXXX on a and b you will get a = 27.