Chọn \(D\) 

Vì : 

\(\dfrac{2}{4}=\dfrac{1}{2}\)

Còn đáp án  \(A,B,C\) không đúng vì : 

\(\dfrac{1}{4}=\dfrac{1}{4}\)

\(\dfrac{-1}{4}=\dfrac{-1}{4}\)

\(\dfrac{-2}{4}=\dfrac{-1}{2}\)

kq sai ạ

\(0,2\times17\times7+0,14\times520+31\times14\)

\(=3,4\times7+0,14\times520+31\times14\)

\(=23,8+0,14\times520+31\times14\)

\(=23,8+72,8+31\times14\)

\(=23,8+72,8+434\)

\(=530,6\)

\(\dfrac{2}{5}+\dfrac{3}{4}=\dfrac{8}{20}+\dfrac{15}{20}=\dfrac{23}{20}\)

\(\dfrac{2}{7}+\dfrac{5}{9}=\dfrac{18}{63}+\dfrac{35}{63}=\dfrac{53}{63}\)

\(\dfrac{4}{7}+\dfrac{3}{4}+\dfrac{2}{7}= \left(\dfrac{4}{7}+\dfrac{2}{7}\right)+\dfrac{3}{4}=\dfrac{6}{7}+\dfrac{3}{4}=\dfrac{45}{28}\)

#lsbdmbtcn

\(a)\)

\(\dfrac{1}{6}+\dfrac{2}{6}+\dfrac{5}{6}=\dfrac{1+2+5}{6}=\dfrac{8}{6}=\dfrac{4}{3}\)

\(b)\)

\(\dfrac{5}{18}+\dfrac{7}{18}+\dfrac{13}{18}=\dfrac{5+7+13}{18}=\dfrac{25}{18}\)

bn tách ra nha

câu \(c)\) bn có thể làm như này nha : 

\(\dfrac{11}{4}\times\dfrac{-4}{11}-\dfrac{5}{4}:\dfrac{11}{4}\)

\(=\dfrac{11}{4}\times\dfrac{4}{11}-\dfrac{-5}{4}\times\dfrac{4}{11}\)

\(=\dfrac{4}{11}\times\left(\dfrac{11}{4}-\dfrac{-5}{4}\right)\)

\(=\dfrac{4}{11}\times\left(-4\right)\)

\(=\dfrac{-16}{11}\)

\(b)\) \(1,6\times2\dfrac{1}{4}-1,6\times3\dfrac{1}{2}\)

\(=1,6\times\dfrac{9}{4}-1,6\times\dfrac{7}{2}\)

\(=1,6\times\left(\dfrac{9}{4}-\dfrac{7}{2}\right)\)

\(=1,6\times\dfrac{-5}{4}\)

\(=-2\)

\(c)\)

\(\dfrac{11}{4}\times\dfrac{-4}{11}-\dfrac{5}{4}:\dfrac{11}{4}\)

\(=\dfrac{11}{4}\times\dfrac{-4}{11}-\dfrac{5}{4}\times\dfrac{4}{11}\)

\(=-1-\dfrac{5}{4}\times\dfrac{4}{11}\)

\(=-1-\dfrac{5}{11}\)

\(=\dfrac{-16}{11}\)