Question 24817
Let the first be y
Let the second be x
Let the third be z
y+x+z=300
x=100+y
x-y=100 (1)


z=100+x
z-x=100 (2)


y+x+z=300
x-y=100 ---(1)
2x+z=400 (set 1)


z-x=100 (2) ---> multiply this equation by  and add it to set 1


2x+z=400
2z-2x=200
3z=600
z=200


200-x=100
x=100

Hence the second one is 100m long.




2.
Neil = 4+x
Andrea = x


four years ago neil's age = 4+x-4
Andreas age four year ago = x-4
2(x-4)=4+x-4
-8+2x=x
x=8


8+4=12
Hence Neil is 12 and Andrea is 8.


3.Consective integers = x, x+1
2(x+x+1)=42
4x+2=42
4x=40
x=10
10+1=11


Hence the two consective integers are 10 and 11.
Paul.