Find the sum:

$\dfrac{-11}{18} + \dfrac{5}{-12}$

First express each rational number with a positive denominator.

$\dfrac{5}{-12} = \dfrac{5 \times (-1)}{-12 \times (-1)} = \dfrac{-5}{12}$

The denominators are different, so express the rational numbers with the LCM of their denominators as the common denominator and then add.

LCM of 18 and 12 = 36

$\dfrac{-11}{18} + \dfrac{-5}{12} = \dfrac{(-11) \times 2 + (-5) \times 3}{36} \\[1em] = \dfrac{-22 - 15}{36} \\[1em] = \dfrac{-37}{36} \\[1em] = -1\dfrac{1}{36}$

Hence, $\mathbf{\dfrac{-11}{18} + \dfrac{5}{-12} = -1\dfrac{1}{36}}$.