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a)<=>2/7:(13/24+5/24) b)<=>15/24-9/24-4/24 c)=7.5.39/13.14.15
<=>2/7:3/4 <=>2/24=1/12 =3/2.3
<=>2/7x4/3 =1/2
<=>8/21
a. \(\frac{2}{7}:\frac{13}{24}+\frac{2}{7}:\frac{5}{24}\)
= \(\frac{2}{7}:\left(\frac{13}{24}+\frac{5}{24}\right)\)
= \(\frac{2}{7}:\frac{3}{4}\)
= \(\frac{8}{21}\)
b. \(\frac{15}{24}-\frac{3}{8}-\frac{1}{6}\)
= \(\frac{15}{24}-\frac{9}{24}-\frac{4}{24}\)
= \(\frac{2}{24}=\frac{1}{12}\)
c. \(\frac{7}{13}.\frac{5}{14}.\frac{39}{15}\)
= \(\frac{7.5.3.13}{13.2.7.3.5}\)
= \(\frac{1}{2}\)

a: \(\frac79-\frac{4}{15}+\frac61\)
\(=\frac{35}{45}-\frac{12}{45}+6\)
\(=6+\frac{23}{45}=\frac{270}{45}+\frac{23}{45}=\frac{293}{45}\)
b: \(\frac{44}{21}-\left(\frac34+\frac{2}{21}\right)\)
\(=\frac{44}{21}-\frac{2}{21}-\frac34\)
\(=2-\frac34=\frac54\)
c: \(\frac{17}{12}+\frac{13}{7}-\frac67+\frac{7}{12}\)
\(=\frac{17}{12}+\frac{7}{12}+\left(\frac{13}{7}-\frac67\right)\)
=2+1
=3

a) \(\frac{21\times11\times2\times17\times4}{11\times17\times21\times3}=\frac{2\times4}{3}_{ }=\frac{8}{3}\)
b)\(\frac{5\times7\times13\times2}{7\times2\times13\times5\times5}=\frac{1}{5}\)
a)\(\frac{21x22x68}{11x17x63}\) = \(\frac{1x2x4}{1x1x3}\) =\(\frac{8}{3}\)
b)\(\frac{5x7x26}{14x13x25}\) = \(\frac{1x1x2}{2x1x5}\) =\(\frac{1x1x1}{1x1x5}\) = \(\frac{1}{5}\)

a)\(\frac{x}{17}=\frac{60}{204}=\frac{5}{17}\Rightarrow x=5\)
b)\(\frac{6+x}{33}=\frac{7}{11}\Rightarrow11\left(6+x\right)=7.33\Rightarrow11.6+11x=231\Rightarrow66+11x=231\)
\(\Rightarrow11x=231-66\Rightarrow11x=165\Rightarrow x=\frac{165}{11}=15\)
c)\(\frac{12+x}{43-x}=\frac{2}{3}\Rightarrow2\left(43-x\right)=3\left(12+x\right)\Rightarrow2.43-2x=3.12+3x\)
\(86-2x=36+3x\Rightarrow86-36=3x+2x\Rightarrow50=5x\Rightarrow x=\frac{50}{5}=10\)

\(\frac{43}{20}+\frac{17}{6}:\left(\frac{5}{8}+\frac{7}{30}\right)\)
\(=\frac{43}{20}+\frac{17}{6}\cdot\frac{120}{103}\)
\(=\frac{43}{20}+\frac{340}{103}\)
\(=\frac{11229}{2060}\)

\(\frac{8}{9}-\frac{5}{6}=\frac{16}{18}-\frac{15}{18}=\frac{1}{18}\)
\(\frac{90}{108}-\frac{40}{72}=\frac{5}{6}-\frac{5}{9}=\frac{15}{18}-\frac{10}{18}=\frac{5}{18}\)
\(\frac{15}{17}-\frac{11}{13}=\frac{195}{221}-\frac{187}{221}=\frac{8}{221}\)
\(\frac{8}{9}-\frac{5}{6}=\frac{16}{18}-\frac{15}{18}=\frac{1}{18}\)
\(\frac{90}{108}-\frac{40}{72}=\frac{30}{36}-\frac{20}{36}=\frac{10}{36}=\frac{5}{18}\)
a) 271,43 : 17 = 15,96 (dư 0,11)
b) 26,7 x 1,5 = 40,05
c) 13,6 + 180 = 193,6
d) 90,203 – 24,086 = 66,117