Question 1120446
Assigning variables and carefully transcribing the description into equations:

<pre>
PERSON    VARIABLE   IN x YEARS
Juanita    J          J+x
Son        y          y+x
Mother     m          m+x
</pre>

The question asks for J.


{{{system(J+x=5y,J+x=m,y+x=8+J,J+m=100)}}}


Steps can be different.  First step could be, substitute for m wherever possible,...


{{{system(J-5y+x=0,-J+y+x=8,2J+x=100)}}}



May find that J is 35.