Solutions; Suppose this rope is x meters long at first,

X-3.6=6.9

x=6.9+3.6

x= 10.5

(2)

Solutions; Set up a tape recorder x yuan,

12X=3360

X=3360/ 12

X=280

(3)

Solutions; Pigeons can fly x meters per hour against the wind.

3X= 120

X= 120/3

X=40

(4)

Solutions; Run a school and send x kilograms of radishes.

2x+ 100=600

2x=600- 100

2x=500

x=500/2

x=250

(5)

Solution: Let Xiaohua have X books.

2X-4=36

2X=36+4

2X=40

X=40/2

X=20

(6)

Solution: Suppose a * * * contains X cylinders.

5X+2= 1377

5x= 1377-2

5x= 1375

x= 1375/5

x=275

275+ 1=276 (pieces)