Data Sufficiency

Today Bill is 13 times as old as Pete. In 9 yeasr Bill will be 4 times as old as Pete. How old will Pete be 2 years from today ?

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OA is C I would like to know why when i do this it does not work:

B + 9 = 4(13P + 9) ----> 13P + 9 = 52P + 36 DOES NOT WORK !

Here is my take:

B=13P(at present)
B+9=4(P+9) (in future), 13P+9 is not pete's age in 9years.

By arranging,=> p=3

hope it can explain.

heshamelaziry wrote:Today Bill is 13 times as old as Pete. In 9 yeasr Bill will be 4 times as old as Pete. How old will Pete be 2 years from today ?

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OA is C I would like to know why when i do this it does not work:

B + 9 = 4(13P + 9) ----> 13P + 9 = 52P + 36 DOES NOT WORK !

not sure how this ended up in the data sufficiency forum, but here goes anyway:

1st equation: B = 13P
2nd equation: B + 9 = 4(P + 9)

Question: what's P + 2?

Subbing B=13P into the 2nd equation:

13P + 9 = 4P + 36
9P = 27
P = 3

and answering the question:

P + 2 = 3 + 2 = 5

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Your mistake is that instead of using P for Pete's age in the 2nd equation, you used 13P (13 times Pete's age).