Question 774061
s = Sarah's age
d = Donald's age


_______________now____________________9 years from now
Sarah__________(1/7)d_________________s+9
Donald_________d______________________d+9



In 9 years, {{{s+9=6+(1/6)(d+9)}}}, and {{{s=(1/7)d}}}.
Think first how that makes sense.
...
When understood, simplify the "(1/6)"-"+9" equation, substitute for s, and solve first for s, before solving for d.


s=-3+(1/6)(d+9)
6s=-18+d+9
6s=d-9
substitute...
{{{6(1/7)d=d-9}}}
6d=7d-63
6d-7d=-63
d=63___________Donald's age
Now find s,
s=d/7
s=63/7
s=9___________Sarah's age


Sarah is 9 and Donald is 63