Question 1107516
Children can come to dinner for free.

c, child price, 0
a, adult price, a

{{{200*0+150a=900}}}


{{{a=6}}}

-


Children not come for free?
{{{200c+150a=900}}}

{{{20c+15a=90}}}

{{{highlight_green(4c+3a=18)}}}-----this is all you can do unless there are other facts to use.  a and c will be greater than 0, and {{{a>c}}}.


You CAN look for whole-number combinations that fit the equation such that {{{a>c}}}.


{{{3a=-4c+18}}}
{{{highlight_green(a=-(4/3)c+6)}}}


If vertical axis is adults price and horizontal axis is children price,
{{{graph(400,400,-1,7,-1,7,-(4/3)x+6)}}}


You can also accept rational values in addition to maybe whole numbers, and pick {{{c<2}}} and find the corresponding a.