2) 180× 2 ÷ 20 = 18cm

3) 3600 ÷ ( 1- 1/4) × 1/4 = 1200.

4)( 1-2/3)÷( 1/ 15+ 1/ 18)

= 1/3÷ 1 1/90

=30/ 1 1 hour

5)(32-4)÷2= 14 trees

6) 10 ÷ 2 = 5m 5+2 = 7m

3. 14×7×7-3. 14×5×5

= 153.86-78.5

=75.36 square meters

7) perimeter: 3. 14×3×2= 18.84 decimeter, area: 3. 14×3×3=28.26 square decimeter.

8)300÷(700-300)=75%

9) 18÷[(7/30- 1/ 15×3)÷2]

= 18÷ 1/60

= 1080

10)40× 15%÷ 10%-40

=60-40

=20 grams

1 1)7+8= 15

24÷( 1/2-7/ 15)

=24÷ 1/30

=720 km

Line B: 720÷( 1+7/8)=384 km.

Line A: 384×7/8=336 km.