Find the sum:

$\dfrac{-5}{12} + \dfrac{7}{-12}$

First express each rational number with a positive denominator.

$\dfrac{7}{-12} = \dfrac{7 \times (-1)}{-12 \times (-1)} = \dfrac{-7}{12}$

Both rational numbers now have the same (positive) denominator 12, so add the numerators keeping the denominator the same.

$\dfrac{-5}{12} + \dfrac{-7}{12} = \dfrac{(-5) + (-7)}{12} \\[1em] = \dfrac{-12}{12} \\[1em] = -1$

Hence, $\mathbf{\dfrac{-5}{12} + \dfrac{7}{-12} = -1}$.