Răspuns:
adunarea e comutativă, deci ca sa nu o luăm razna, vom lua câte 2 elemente la adunare:
[tex] - \frac{1}{5} + \frac{24}{3} = \frac{ - 1 \times 3 + 24 \times 5}{15 } = \frac{ - 3 + 120}{15} = \frac{117}{15} \\ \frac{117}{15} + \frac{ - 15}{ - 5} = \frac{117}{15} + \frac{15}{5} (amplificam \: a \: doua \: fractie \: cu \: 3 \: ca \: sa \: eglam \: numitorii) = \frac{117 + 45}{15} = \frac{162}{15} \\ \frac{162}{15} = \frac{162}{15} + \frac{17}{10} (egalam \: numitorii \: la \: 30) = \frac{162 \times 2 + 17 \times 3}{30} = \frac{324 + 51}{30} = \frac{375}{30} \\ - 0.5 = - \frac{1}{2} si \: daca \: adunam \: \frac{1}{2} obtinem \: 0 \: deci \ suma \: ramane \: \frac{375}{30} \\ \\ \frac{375}{30} + 7 \frac{375 + 7 \times 30}{30} = \frac{375 + 210}{30} = \frac{585}{30} = \frac{39}{2} [/tex]
