Let A and B be the following fractions:
[tex]\begin{gathered} A=\frac{m}{q} \\ B=\frac{n}{p} \\ p,q\ne0 \end{gathered}[/tex]if we add A and B, we get:
[tex]A+B=\frac{m}{q}+\frac{n}{p}=\frac{mp+nq}{pq}[/tex]therefore, the sum of two rational numbers is a rational number