\(a,\dfrac{3}{4}-\dfrac{2}{7}=\dfrac{13}{28}\\ b,\dfrac{3}{8}-\dfrac{5}{16}=\dfrac{1}{16}\\ c,\dfrac{7}{5}-\dfrac{2}{3}=\dfrac{11}{15}\\ d,\dfrac{31}{36}-\dfrac{5}{6}=\dfrac{1}{36}\)

\(a,\dfrac{3}{4}-\dfrac{2}{7}=\dfrac{21}{28}-\dfrac{8}{28}=\dfrac{13}{28}\)

\(b,\dfrac{3}{8}-\dfrac{5}{16}=\dfrac{6}{16}-\dfrac{5}{16}=\dfrac{1}{16}\)

\(c,\dfrac{7}{5}-\dfrac{2}{3}=\dfrac{21}{15}-\dfrac{10}{15}=\dfrac{11}{15}\)

\(d,\dfrac{31}{36}-\dfrac{5}{6}=\dfrac{31}{36}-\dfrac{30}{36}=\dfrac{1}{36}\)

a: =735+23-135+177=600+200=800

b: =124-312+76-112+21=200-424+21=-203

c: =183+21+65-183-21=65

d: \(=-271+37-160+31-137=-500\)

e: =-3a+b-3c+b+3c+2a-2b

=-a

a)  32x31+69x31-31 

=992+2070

=3062

b)  43x166+14x83

=7138+1162

=8300

c)  7/2-3/2:x=5/4

            3/2:x=7/2-5/4

            3/2:x= 9/4

                   x=3/2:9/4

                   x= 2/3

giúp mình vứi

`31/4:2=31/4*1/2=31/8`

a) = \(\left(\dfrac{2}{7}+\dfrac{4}{7}+\dfrac{1}{7}\right):\dfrac{27}{31}\)

= \(\dfrac{7}{7}\) x \(\dfrac{31}{27}\)

= 1 x \(\dfrac{31}{27}\) = \(\dfrac{31}{27}\)

b) = \(\left(\dfrac{23}{45}:\dfrac{23}{45}\right)\)x \(\dfrac{17}{51}\)

= 1 x \(\dfrac{17}{51}\)= \(\dfrac{17}{51}\)