Chapter R - Review of Basic Concepts - R.2 Real Numbers and Their Properties - R.2 Exercises - Page 20: 31

$-\frac{25}{36}$

$$(-\frac{2}{9}-\frac{1}{4})-[-\frac{5}{18}-(-\frac{1}{2})]$$ $$=(-\frac{8}{36}-\frac{9}{36})-(-\frac{5}{18}+\frac{9}{18})$$ $$=-\frac{17}{36}-\frac{4}{18}$$ $$=-\frac{17}{36}-\frac{8}{36}$$ $$=-\frac{17}{36}-\frac{8}{36}$$ $$=-\frac{25}{36}$$