Chu vi mảnh vườn hình chữ nhật là
(5,5 + 3,75) . 2 = 18,5 (m)

Số khóm hoa cần trồng là:

18,5: \(\dfrac{1}{4}\)=74 (khóm)

Đáp số: 74 khóm

a)\(\dfrac{1}{5}\)+\(\dfrac{4}{5}\):x=0,75                       b)x+\(\dfrac{1}{2}\)=1-x

\(\dfrac{4}{5}\):x=0,75-\(\dfrac{1}{5}\)                             x=1-\(\dfrac{1}{2}\)

\(\dfrac{4}{5}\):x=\(\dfrac{11}{20}\)                                   x=\(\dfrac{1}{2}\)

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

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

b)2.(\(\dfrac{-3}{2}\))\(^2\)-\(\dfrac{7}{2}\)=2.\(\dfrac{9}{4}\)-\(\dfrac{7}{2}\)=\(\dfrac{9}{2}\)-\(\dfrac{7}{2}\)= 1

c)\(\dfrac{-3}{4}\).5\(\dfrac{3}{13}\)-0,75.\(\dfrac{36}{13}\)=\(\dfrac{-3}{4}\).\(\dfrac{68 }{13}\)-\(\dfrac{3}{4}\).\(\dfrac{36}{13}\)=\(\dfrac{-51}{13}\)-\(\dfrac{27}{13}\)=-6

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

2.\(\dfrac{9}{4}\)-\(\dfrac{7}{2}\)=\(\dfrac{9}{2}\)-\(\dfrac{7}{2}\)=1

\(\dfrac{-3}{4}\). \(\dfrac{68}{13}\)-\(\dfrac{3}{4}\).\(\dfrac{36}{13}\)=\(\dfrac{-51}{13}\)-\(\dfrac{27}{13}\)=-6