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Teach me math problems
1、 1/2+( 1/2+ 1/3)+(2/3+ 1/4)+(3/4+ 1/5)+(4/5+ 1/6)+……+( 18/ 19+ 1/20)

= 18+ 1/20

= 18 and 1/20

2. Let the odd numbers removed be A and a+32.

Then1+3+5+7+... 49-a-(a+32) = 24 and 1 1/23*23.

625-32-2a=563

A= 15 The other even number is 47.

3. The total length is x kilometers.

( 1/70x+40)*50=x

x=7000

4.a/b= 15/7 means 7a= 15b.

(a+ 12)/b=9,a=9b- 12。

So a= 15/4 b=7/4.

5. let the subtrahend be x.

Negative+negative+difference =2 (negative+difference)

So 2(x+x/(3/4))=280.

x=60

6. If the second workshop is X, then the first workshop is 4/5x-30.

3/4(x- 10)= 4/5x-30+ 10

x=550

Workshop 1 4 10

7. Set the distance of x kilometers.

A drives x+ 120 and B drives 2x- 120.

At the same time, the distance is proportional to the speed.

(x+ 120)/(2x- 120)= 7:9

x=384

8. Warehouse B is X and Warehouse A is x+9 1.2.

x*(65%-35%)=9 1.2

x=304

A warehouse 395.2.

9. pour out v cubic centimeters

Its height is V/72 in a square volume and V/48 in a cylindrical volume.

The height of residual water per square volume is 30v/72.

30 volts /72 = 5 volts /48

V=864 cubic centimeters

The divisors of 10 and 1690 are 2,5, 13 and 13.

The common factor of two numbers is 13, so these two numbers may be 2* 13 and 5* 13 or 2*5* 13 and 13.

Namely 26 and 65 or 130 and 13.

1 1, the title is unclear.

B where does it go from b?