Explicație pas cu pas:
[tex]a \: si \: - \frac{5}{12} \\ \\ | - \frac{5}{12} | + a = \frac{2}{3} \\ \frac{5}{12} + a = \frac{2}{3} \\ a = {}^{4)} \frac{2}{3} - \frac{5}{12} \\ a = \frac{8}{12} - \frac{5}{12} \\ a = \frac{3}{12} {}^{(3} = \frac{1}{4} [/tex]
Succes!