SOLUTION: Sarah is 2 times as old as Bob, 6 years ago Sarah was 4 times as old as Bob, how old is Bob now ?

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Question 978480: Sarah is 2 times as old as Bob, 6 years ago Sarah was 4 times as old as Bob, how old is Bob now ?
Answer by Cromlix(4381) About Me  (Show Source):
You can put this solution on YOUR website!
Hi there,
Sarah is 2 times as old as Bob,
S = 2B
6 years ago Sarah was 4 times as old as Bob
S - 6 = 4(B - 6)
Substitute 2B for S From first equation
2B - 6 = 4(B - 6)
Multiply out brackets
2B - 6 = 4B - 24
Collect like terms
2B - 4B = - 24 + 6
- 2B = - 18
B = -18/-2
B = 9
Therefore Bob is 9 yrs old at present
Hope this helps:-)