Giải

Tính chu vi mảnh vườn

                   Chu vi =2*(5.5m+3,75m)=2*9,25m=18,5

Số khóm hoa cần trồng

Số khóm hoa = chu vi / khoảng cách giữa các khóm hoa =18,5/(1/4)m=18,5*4

                                                                     =74 khóm hoa

A)0,75=3/4                                                   B)2x+1/2=1                            

1/5+4/5x=3/4                                                 2x=1-1/2=1/2

4/5x=3/4-1/5=15-4/20=11/20                        x=1/2:2=1/4

4.20=11.5x                                                     =1/4

80/55=16/11=16/11

A) 2/3.5/4-3/4.2/3

2/3.(5/4-3/4)

2/3.2/4=2/3.1/2=1/3

B)2.(-3/2)2-7/2

2.9/4-7/2

18/4-7/2

18/4-14/4

4/4=1

C)-3/4.5 3/13-0,75.36/13

-3/4.68/13-0,75.36/13

-3/4.68/13-3/4.36/13

-3/4.(68/13+36/13)

-3/4.104/13

-3/4.8=-3.2=-6