SOLUTION: John is six times as old as his little sister Anna. In twelve years,John will be twice as old as Anna. How old is John now ? Okay this is just an example of what I'm having to do a

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Question 1059743: John is six times as old as his little sister Anna. In twelve years,John will be twice as old as Anna. How old is John now ? Okay this is just an example of what I'm having to do and it shows the following.
6x + 12=2(x+12)
6x+12=2x+24
4x=12
X=3
So the question is I'm not understanding how they came about getting 4x=12 or even 6x+12=2x+24?
Found 2 solutions by Fombitz, ikleyn:
Answer by Fombitz(32388) About Me  (Show Source):
You can put this solution on YOUR website!
Assume Anna is x years old.
So then, John is 6x years old.
In twelve years, John will be 6x+12 years old and Anna will be x+12 years old.
So in twelve years, John will be twice as old as Anna,
6x%2B12=2%28x%2B12%29
6x%2B12=2x%2B24
Subtract 2x+12 from both sides,
6x%2B12-2x-12=2x%2B24-2x-12
4x=12
Divide both sides by 4,
%284x%29%2F4=12%2F4
%284%2F4%29x=3
%281%29x=3
x=3

Answer by ikleyn(52787) About Me  (Show Source):
You can put this solution on YOUR website!
.
Try to read the lesson
    - HOW TO solve a linear equation
in this site.