\(a,\dfrac{3}{8}.19\dfrac{1}{3}-\dfrac{3}{8}.33\dfrac{1}{3}\)
\(=\dfrac{3}{8}.\left(19\dfrac{1}{3}-33\dfrac{1}{3}\right)\)
\(=\dfrac{3}{8}.\left(\dfrac{58}{3}-\dfrac{100}{3}\right)\)
\(=\dfrac{3}{8}.\dfrac{-42}{3}\)
\(=\dfrac{-42}{8}=\dfrac{-21}{4}\)
\(b,\dfrac{21}{47}+\dfrac{9}{45}+\dfrac{26}{47}+\dfrac{4}{5}\)
\(=\left(\dfrac{21}{47}+\dfrac{26}{47}\right)+\left(\dfrac{9}{45}+\dfrac{4}{5}\right)\)
\(=\dfrac{47}{47}+\left(\dfrac{9}{45}+\dfrac{36}{45}\right)\)
\(=1+\dfrac{45}{45}\)
\(=1+1\)
\(=2\)
\(c,\dfrac{13}{25}+\dfrac{6}{41}-\dfrac{38}{25}+\dfrac{35}{41}-\dfrac{1}{2}\)
\(=\left(\dfrac{13}{25}-\dfrac{38}{25}\right)+\left(\dfrac{6}{41}+\dfrac{35}{41}\right)-\dfrac{1}{2}\)
\(=\dfrac{-25}{25}+\dfrac{41}{41}-\dfrac{1}{2}\)
\(=-1+1-\dfrac{1}{2}\)
\(=0-\dfrac{1}{2}\)
\(=\dfrac{-1}{2}\)
\(d,12,5.\left(\dfrac{-5}{7}\right)+1,5.\left(\dfrac{-5}{7}\right)\)
\(=\dfrac{-5}{7}.\left(12,5+1,5\right)\)
\(=\dfrac{-5}{7}.14\)
\(=-10\)
