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Let the first be y
Let the second be x
Let the third be z
2x+z=400 (set 1)
z-x=100 (2) ---> multiply this equation by and add it to set 1
Hence the second one is 100m long.
Neil = 4+x
Andrea = x
four years ago neil's age = 4+x-4
Andreas age four year ago = x-4
Hence Neil is 12 and Andrea is 8.
3.Consective integers = x, x+1
Hence the two consective integers are 10 and 11.