Is the difference between two rational numbers always rational number

Hello,

An integer is a rational number (ex 5=5/1=10/2 ...)

The sum of 2 rationals is a rational.

Substract a rational is adding its opposite.

The difference of 2 rationals is always a rational (substraction is a intern law)

Not always. It depends on the teacher and the school. Depends on the rules and how your being tought.