explanation - if you do 2408 plus 557 that would be 2965 but then 379 come off board so you do 2965 take away 379 that leads to 2586 and if 658 are kids u do 2586 take away 658 which leads to 1928 adults
When the 2 graphs are the same. It'll be infinitely many solutions.
System Equations are to find the intercepts of graphs so just think that when 2 graphs are same, that means they both intercept each others infinitely.