lời giải

chu vi khu vườn là:

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

số khóm hoa cần trồng là

18,5:\(\dfrac{1}{4}\)=74(khóm hoa)

            đáp số: 74 khóm hoa

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

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

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

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

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

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

a.\(\dfrac{2}{3}\).\(\dfrac{5}{4}\)-\(\dfrac{3}{4}\).\(\dfrac{2}{3}\)               b.2.(-\(\dfrac{3}{2}\))\(^2\)-\(\dfrac{7}{2}\)             c.-\(\dfrac{3}{4}\).5\(\dfrac{3}{13}\)-0,75.\(\dfrac{36}{13}\)

=\(\dfrac{2}{3}\).(\(\dfrac{5}{4}\)-\(\dfrac{3}{4}\))                   =2.\(\dfrac{9}{4}\)-\(\dfrac{7}{2}\)                  =-\(\dfrac{3}{4}\).\(\dfrac{68}{13}\)-\(\dfrac{3}{4}\).\(\dfrac{36}{13}\)

=\(\dfrac{2}{3}\).\(\dfrac{2}{4}\)                          =\(\dfrac{9}{2}\)-\(\dfrac{7}{2}\)                     =-\(\dfrac{3}{4}\).(\(\dfrac{68}{13}\)+\(\dfrac{36}{13}\))

=\(\dfrac{1}{3}\)                              =1                           =-\(\dfrac{3}{4}\).8

                                                                   =-6