Solution:
a+5=10+b
a-b=5
It means subtraction of two numbers is 5 which is rational.
It is only possible when:
(a) Both a and b are rationals, for example: 12-7 = 5
(b) Both a and b are irrationals, for example: [5+root(2)]- root(2) = 5
So any one of a and b cannot be irrational, either both must be irrational or rational according to this equation.