Question 286180
<pre><font size = 4 color = "indigo"><b>
Let x = Jane's age now.

Jane was 12 when Jessica was Jane's present age, x.

Let y = the number of years ago it's been since Jane was 12
and Jessica was x. 

Jessica's age y years ago = Jane's age now.

                   24 - y = x

   Jane's age y years ago = 12

                    x - y = 12

So we have this system:

{{{system(24-y=x, x-y=12)}}}

Can you solve that system?  If not post again asking how,

x=18, y=6

So Jane is 18 years old now.  

Checking:  y=6 years ago, Jane was 12, and Jessica was 18. Today
Jessica is twice 12, Jane's age then.

Edwin</pre>