[tex](( \frac{1}{2} + \frac{1}{21} ) \div ( \frac{1}{18} + \frac{1}{14}) - 2 \frac{1}{2} ) \times 8[/tex]
[tex] = ( \frac{21 + 2}{42} \div \frac{14 + 18}{252} - \frac{2 \times 2 + 1}{2} ) \times 8[/tex]
[tex] = ( \frac{23}{42} \div \frac{32}{252} - \frac{5}{2} ) \times 8[/tex]
[tex] = ( \frac{23}{42} \times \frac{252}{32} - \frac{5}{2} ) \times 8[/tex]
252se imparte la 42 si ramane 6
[tex] = ( \frac{23 \times 6}{1 \times 32} - \frac{5}{2} ) \times 8[/tex]
[tex] = ( \frac{138}{32} - \frac{5}{2}) \times 8 = \frac{138 - 16 \times 5}{32} \times 8[/tex]
[tex] = \frac{138 - 80}{32} \times 8 = \frac{58}{32} \times 8 = \frac{58 \times 1}{4} = [/tex]
[tex] = \frac{58}{4} \div |2| = \frac{29}{2} [/tex]
