a)\(\dfrac{7}{2}\) - (\(\dfrac{3}{4}\)+\(\dfrac{1}{5}\))

=\(\dfrac{7}{2}\) - \(\dfrac{19}{20}\)

=\(\dfrac{51}{20}\)

b)\(\dfrac{12}{23}\).\(\dfrac{7}{13}\)+\(\dfrac{11}{23}\).\(\dfrac{7}{13}\)

=\(\dfrac{7}{13}\).(\(\dfrac{12}{23}\)+\(\dfrac{11}{23}\))

=\(\dfrac{7}{13}\).1 =\(\dfrac{7}{13}\)

c)\(|-2|\)-(\(\dfrac{5}{9}\)-\(\dfrac{2}{3}\))\(\div\dfrac{4}{27}\)

=2+\(\dfrac{1}{9}\).\(\dfrac{27}{4}\)

=2+\(\dfrac{3}{4}\)

=2,75 hoặc \(\dfrac{11}{4}\)

Chu vi mảnh vườn đó là:

(5,5+3,75)x2=18,5(m)=\(\dfrac{37}{2}\)m

Số khóm hoa cần trồng là:

\(\dfrac{37}{2}\div\dfrac{1}{4}=24\)(khóm hoa)

Đáp số: 24 khóm hoa

a)\(\dfrac{1}{5}+\dfrac{4}{5}\div x=0,75\)

\(\dfrac{4}{5}\div x=\dfrac{11}{20}\)

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

b)\(x+\dfrac{1}{2}=1-x\)

\(x+x=1-\dfrac{1}{2}\)

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

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

�+12=1−


 

a)\(\dfrac{1}{5}+\dfrac{4}{5}\div x=0,75\)

\(\dfrac{4}{5}\div x=\dfrac{11}{20}\)

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

b)\(x+\dfrac{1}{2}=1-x\)

\(x+x=1-\dfrac{1}{2}\)

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

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

�+12=1−


 

a)\(\dfrac{1}{5}+\dfrac{4}{5}\div x=0,75\)

\(\dfrac{4}{5}\div x=\dfrac{11}{20}\)

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

b)\(x+\dfrac{1}{2}=1-x\)

\(x+x=1-\dfrac{1}{2}\)

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

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

�+12=1−


 

a)\(\dfrac{1}{5}+\dfrac{4}{5}\div x=0,75\)

\(\dfrac{4}{5}\div x=\dfrac{11}{20}\)

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

b)\(x+\dfrac{1}{2}=1-x\)

\(x+x=1-\dfrac{1}{2}\)

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

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

�+12=1−


 

\(\dfrac{2}{3}\times\dfrac{5}{4}-\dfrac{3}{4}\times\dfrac{2}{3}\)

\(\dfrac{2}{3}\times\left(\dfrac{5}{4}-\dfrac{3}{4}\right)\)

\(\dfrac{2}{3}\times\dfrac{1}{2}\)

\(\dfrac{1}{3}\)

b)\(2\times\left(\dfrac{-3}{2}\right)^2-\dfrac{7}{2}\)

\(2\times\dfrac{9}{4}-\dfrac{7}{2}\)

\(\dfrac{18}{4}-\dfrac{14}{4}\)

1

c)\(-\dfrac{3}{4}\times5\dfrac{3}{13}-0,75\times\dfrac{36}{13}\)

\(\dfrac{-3}{4}\times\dfrac{68}{13}-\dfrac{3}{4}\times\dfrac{36}{13}\)

\(\dfrac{3}{4}\times\dfrac{-68}{13}-\dfrac{3}{4}\times\dfrac{36}{13}\)

\(\dfrac{3}{4}\times\left(\dfrac{-68}{13}-\dfrac{36}{13}\right)\)

\(\dfrac{3}{4}\times\left(\dfrac{-8}{1}\right)\)

-9