[attach]92106[/attach] L esercizio n249 non riesco. Grazie

249) [attach]92198[/attach] ========================================================= (- dfrac {7}{12}+ dfrac {3}{5}- dfrac {1}{6})-(- dfrac {3}{4}+ dfrac {8}{5}- dfrac {3}{2})+(- dfrac {11}{15}- dfrac {7}{4}+1+ dfrac {3}{20})=$ $=( dfrac {-35+36-10}{60})-( dfrac {-15+32-30}{20})+( dfrac {-44-105+60+9}{60})=$ $=(- dfrac {9}{60})-(- dfrac {13}{20})+(- dfrac {80}{60})=$ $=(- dfrac { cancel 9^3}{ cancel {60}_{20}})+ dfrac {13}{20}+(- dfrac { cancel {80}^4}{ cancel {60}_3})=$ $=(- dfrac {3}{20})+ dfrac {13}{20}+(- dfrac {4}{3})=$ $= dfrac {10}{20}- dfrac {4}{3}=$ $= dfrac { cancel {10}^1}{ cancel {20}_2}- dfrac {4}{3}=$ $= dfrac {1}{2}- dfrac {4}{3}=$ $= dfrac {3-8}{6}=$ $=- dfrac {5}{6}

[attach]126997[/attach] (-75+80+96)/60 - (30-14+1)/20 + (165-51-100)/60 (-75+80+96-90+42-3+165-51-100)/60 64/60 16/15

[attach]126998[/attach] 4/9 - (20+33-7)/12 + 26/9 - (-5+9-24)/12 16/36 - (60+99-21)/36 + 104/36 - (-15+27-72)/36 (16-60-99+21+104+15-27+72)/36 42/36 7/6

Aiuto

249)

=========================================================

$\left(-\dfrac{7}{12}+\dfrac{3}{5}-\dfrac{1}{6}\right)-\left(-\dfrac{3}{4}+\dfrac{8}{5}-\dfrac{3}{2}\right)+\left(-\dfrac{11}{15}-\dfrac{7}{4}+1+\dfrac{3}{20}\right)=$

$=\left(\dfrac{-35+36-10}{60}\right)-\left(\dfrac{-15+32-30}{20}\right)+\left(\dfrac{-44-105+60+9}{60}\right)=$

$=\left(-\dfrac{9}{60}\right)-\left(-\dfrac{13}{20}\right)+\left(-\dfrac{80}{60}\right)=$

$=\left(-\dfrac{\cancel9^3}{\cancel{60}_{20}}\right)+\dfrac{13}{20}+\left(-\dfrac{\cancel{80}^4}{\cancel{60}_3}\right)=$

$=\left(-\dfrac{3}{20}\right)+\dfrac{13}{20}+\left(-\dfrac{4}{3}\right)=$

$=\dfrac{10}{20}-\dfrac{4}{3}=$

$=\dfrac{\cancel{10}^1}{\cancel{20}_2}-\dfrac{4}{3}=$

$=\dfrac{1}{2}-\dfrac{4}{3}=$

$=\dfrac{3-8}{6}=$

$=-\dfrac{5}{6}$