Let $\pm$ be the D604: Integer addition operation.

Let $\cdot$ be the D608: Integer multiplication operation.

The

**rational addition operation**is the D554: Binary operation \begin{equation} + : \mathbb{Q} \times \mathbb{Q} \to \mathbb{Q}, \quad [(a, b)] + [(c, d)] = [(a d + b c, b d)] \end{equation}