1) To add or subtract fractions, let's firstly check the denominators
In this case, the denominator is the same.
The plus before the bracket does not change the sign.
[tex]\begin{gathered} -\frac{2}{13}+(-\frac{1}{13}) \\ \frac{-2-1}{13} \\ \\ \frac{-3}{13} \end{gathered}[/tex]That is why we get to -3/13 as a result.
