Question 1105553
beth is 11 years old. 

{{{matrix(1,5,
(matrix(2,1,"Beth's",age)),
"",
""="",
"",
11
)}}}
<pre>
B = 11
</pre>
Sandra is Alice's age older than beth. 
<pre>
{{{matrix(1,7,
(matrix(3,1,"Sandra's","",age)),
"",
""="",
"",
(matrix(3,1,"Beth's","",age)),
""+"",
(matrix(3,1,"Alice's","",age))
)}}}

S = B + A
</pre>
Alice is half the age beth will be next year. how old is sandra.
<pre>
{{{matrix(1,5,
(matrix(3,1,"Alice's","",age)),
"",
""="",
"",
expr(1/2)*(matrix(3,3,"Beth's","","","",""+"",1,age,"",""))
)}}}

A = {{{1/2}}}(B + 1)

So we have:

{{{system(B=11,S=B+A,A=expr(1/2)(B+1))}}}

Everywhere there's a B, put 11

{{{system(11=11,S=11+A,A=expr(1/2)(11+1))}}}

We can dispense with 11=11

{{{system(S=11+A,A=expr(1/2)(11+1))}}}

Add the 11+1 and replace it by 12

{{{system(S=11+A,A=expr(1/2)(12))}}}

Multiply the 1/2 by the 12 and get A=6

{{{system(S=11+A,A=6)}}}

Replace the A by 6 in S = 11+A:

S = 11+6

S = 17

So Sandra is 17.

Edwin</pre>