Lm kiểu j vậy apppp chỉ với

Giải thích các bước giải:

Bài 1:

a.$\dfrac14+\dfrac25-\dfrac3{10}=\dfrac{5}{20}+\dfrac{8}{20}-\dfrac{6}{20}=\dfrac{5+8-6}{20}=\dfrac{7}{20}$ 

b.$\dfrac37+\dfrac5{14}-\dfrac12=\dfrac{6}{14}+\dfrac{5}{14}-\dfrac{7}{14}=\dfrac{6+5-7}{14}=\dfrac{4}{14}=\dfrac{2}{7}$

c.$\dfrac79-(\dfrac13+\dfrac29)=\dfrac{7}{9}-\dfrac{5}{9}=\dfrac{2}{9}$

d.$(\dfrac23+\dfrac34)-(\dfrac56-\dfrac18)=\dfrac{17}{12}-\dfrac{17}{24}=\dfrac{17}{24}$

Bài 2:

a.$(\dfrac45\cdot\dfrac{10}{12}):\dfrac23=(\dfrac45\cdot \dfrac56)\cdot \dfrac32=\dfrac23\cdot\dfrac32=1$

b.$\dfrac79:(\dfrac{14}{27}\cdot \dfrac32)=\dfrac79:\dfrac79=1$

c.$\dfrac38\cdot (\dfrac23+\dfrac43)=\dfrac38\cdot 2=\dfrac34$

d.$(\dfrac3{10}+\dfrac6{10})\cdot \dfrac59=\dfrac9{10}\cdot\dfrac59=\dfrac12$

Bài 3:

a.$(\dfrac35+\dfrac23):\dfrac{11}{15}=\dfrac{19}{15}\div \:\dfrac{11}{15}=\dfrac{19}{11}$

b.$\dfrac47\cdot (\dfrac34-\dfrac12)+\dfrac17=\dfrac{4}{7}\cdot \:\dfrac{1}{4}+\dfrac{1}{7}=\dfrac{1}{7}+\dfrac{1}{7}=\dfrac27$

c.$(\dfrac25+\dfrac3{10})\cdot(\dfrac56-\dfrac13)=\dfrac{7}{10}\cdot \:\dfrac{1}{2}=\dfrac{7}{20}$

d.$(\dfrac12+\dfrac23+\dfrac34):\dfrac{19}{12}=(\dfrac{6}{12}+\dfrac{8}{12}+\dfrac{9}{12})\cdot \dfrac{12}{19}=\dfrac{23}{12}\cdot \dfrac{12}{19}=\dfrac{23}{19}$