Chu vi của mảnh vườn là :

(5,5+3,75).2=18,5 (m)

Số khóm hoa cần trồng là :

\(18,5:\dfrac{1}{4}=74\left(Cây\right)\)

Vậy số khóm cây cần trồng là 74 cây

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

\(\dfrac{4}{5}:x=0,75-\dfrac{1}{5}\)

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

   \(x=\dfrac{4}{5}:\dfrac{11}{20}\)

   \(x=\dfrac{4}{5}.\dfrac{20}{11}\)

   \(x=\dfrac{16}{11}\)

Vậy x =\(\dfrac{16}{11}\)

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

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

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

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

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

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

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

Vậy x = \(\dfrac{1}{4}\)

=

c)\(-\dfrac{3}{4}.5\dfrac{3}{13}-0,75.\dfrac{36}{13}\)

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

=\(—\dfrac{3}{4}.\left(\dfrac{68}{13}-\dfrac{36}{13}\right)\)

=\(-\dfrac{3}{4}.2\)

=\(-\dfrac{3}{2}\)

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

=\(2.\dfrac{9}{4}-\dfrac{7}{2}\)

=\(\dfrac{9}{2}-\dfrac{7}{2}\)

=1

a) \(\dfrac{2}{3}\).\(\dfrac{5}{4}-\)\(\dfrac{3}{4}.\dfrac{2}{3}\)23.54−34.23

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

=\(\dfrac{2}{3}.\dfrac{1}{2}\)

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