Question

Vă rog! ! ! ! ! ! ! ! ! ! !

Answer 1

$-\frac{3}{21} - [\frac{5}{42}  - \frac{1}{14}  - \frac{2}{21}]\\ = -\frac{3}{21} - [\frac{5-3-4}{42} \\= -\frac{3}{21} + \frac{2}{21} \\= \frac{5}{21}$