Dọc theo chiều dài, ta trồng được:

\(5,5:\dfrac{1}{4}=22\)(m)

dọc theo chiều rộng,ta trồng được:

\(3,75:\dfrac{1}{4}=15\)(m)

chu vi mảnh vườn là:

(22 + 15).2=74(m)

Số khóm hoa cần trồng là:

74 - 4 = 70(khóm hoa)

vậy khóm hoa cần trồng là 70 khóm hoa

a) \(\dfrac{1}{5}+\dfrac{4}{5}:x=0,75\\ \dfrac{1}{5}+\dfrac{4}{5}:x=\dfrac{3}{4}\\ \dfrac{4}{5}:x=\dfrac{3}{4}-\dfrac{1}{5}\\ \dfrac{4}{5}:x=\dfrac{11}{20}\\ x=\dfrac{11}{20}.\dfrac{4}{5}\\ x=\dfrac{11}{25}\)

b)\(x+\dfrac{1}{2}=1-x\\ 2x=1-\dfrac{1}{2}\\ 2x=\dfrac{1}{2}\\ x=\dfrac{1}{2}:2=\dfrac{1}{4}\)

a) \(\dfrac{2}{3}.\dfrac{5}{4}-\dfrac{3}{4}.\dfrac{2}{3}=\dfrac{5}{6}-\dfrac{3}{6}=\dfrac{2}{6}=\dfrac{1}{3}\)

b)\(2.\left(\dfrac{-3^2}{2}\right)-\dfrac{7}{2}=2.\left(\dfrac{-6}{4}\right)-\dfrac{7}{2}=-3-\dfrac{7}{2}=\dfrac{-13}{2}\)

c)\(\dfrac{-3}{4}.5\dfrac{3}{13}-0,75.\dfrac{36}{13}=\dfrac{-3}{4}.\dfrac{68}{13}-\dfrac{3}{4}.\dfrac{36}{13}=\dfrac{-51}{13}-\dfrac{27}{13}=\dfrac{-78}{13}\)