Diện tích mảnh vườn là:

(5,5+3,75)*2=18,5 (m)

Số khóm hoa cần trồng

18,5:\(\dfrac{1}{4}=74\)( khóm hoa)

A)\(\dfrac{1}{5}+\dfrac{4}{5}:x\dfrac{3}{4}\)                  B)\(x+\dfrac{1}{2}=1-x\\ x+x=1-\dfrac{1}{2}\\ 2x=1-\dfrac{1}{2}\\ 2x=\dfrac{1}{2}\\ x=\dfrac{1}{2}:2\\ x=\dfrac{1}{4}\)

\(\dfrac{4}{5}:x=\dfrac{3}{4}-\dfrac{1}{5}\)

\(\dfrac{4}{5}:x=\dfrac{15-4}{20}\)

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

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

\(x=\dfrac{4}{5}\cdot\dfrac{20}{11}=\dfrac{16}{11}\)

A)\(\dfrac{2}{3}\)*(\(\dfrac{5}{4}\)-\(\dfrac{3}{4}\))      B)\(2\cdot\dfrac{9}{4}-\dfrac{7}{2}\)=\(\dfrac{18}{4}-\dfrac{7}{2}=\dfrac{18}{4}-\dfrac{14}{4}=\dfrac{4}{4}=1\)       C)\(\)\(\dfrac{36}{13}\)\(=\dfrac{3}{4}\cdot\left(\dfrac{-68}{13}-\dfrac{36}{13}\right)=\dfrac{3}{4}\cdot\left(-8\right)=-6\)

= \(\dfrac{2}{3}\cdot\dfrac{2}{4}\)

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