Question 1058127
y adults, s students, c children;


This year:  {{{system(y+s+c=400,12y+9s+5c=3215)}}}


Next year:  {{{15y+10s+6c=3817}}}


Arrange this system and try to use row reduction of the system as a matrix:
{{{system(y+s+c=400,12y+9s+5c=3215,15y+10s+6c=3817)}}}.