Question 983390
x, child price
y, senior price
-
{{{PRICE*QUANTIY=COST}}}


Cost and revenue mean the same for purposes of the question  (this one; not any in general).


Day 1
{{{2x+4y=80}}} which simplified becomes  {{{x+2y=40}}}.


Day 2
{{{7x+5y=145}}}



The system to solve:
{{{system(x+2y=40,7x+5y=145)}}}





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y=15