[RESOLVED] Getting negative instead of positive

I am not sure if this is OK to post this question here because it isn't related to programming, but I was hoping someone could help me out. Sorry, if this is only for programming.

I bought a book to help with algebra, and I am having a hard time understanding why I am getting this question wrong.

This is the story problem.

A mother is 4 times older than her daughter. In 14 years, she will be twice as old as her daughter. Find their ages now.

This is the equation I have.

m is mother. d is daughter.

m = 4d
m+14 = 2d

So then I replace m with 4d and get 4d + 14 = 2d.

To solve for d I subtract 2d from both sides and subtract 14 from both sides. I get.

2d = -14

Then I divide both sides by 2 and get d = -7. So m = 4(-7). So m = -28.

Now, I know that isn't right....because I looked at the answers:eek: . It is actually the correct numbers, but it obviously can't be negative. I am just having a really hard time finding out how to keep them from being negative.

I would be very grateful if someone could tell me what I am doing wrong.

Thank you.

Wouldn't the 2 equations be (since u for got that her daughter would've aged in the 14 years too):

m = 4d
m + 14 = 2(d + 14)

I think this would give the correct result.

Yes, that worked. Thank you very much. I remember thinking that the 14 should be added to both, but I dismissed it because I couldn't figure out how I would make the equation. What you have makes sense, and it worked right.

Thank you.