Question 1165627
{{{system(y+x=113,y-9=4(x-9))}}}



x for Autumn
y for Isaac


{{{x=113-y}}}
Substitute that:
{{{y-9=4((113-y)-9)}}}
{{{y-9=4(104-y)}}}
{{{y-9=416-4y}}}
{{{5y-9=416}}}
{{{5y=425}}}
{{{y=425/5}}}
{{{highlight(y=85)}}}


This could be solved in other ways.
(Recheck the answer to be sure.)