Question 1147894
PRICE,  3 dollars per person
QUANTITY, 30 persons
COST, 150 dollars


{{{PQ=C}}}


Note that {{{3*30<>150}}}, but instead {{{3*30=90}}}


Better would be, there is a minimum base cost no matter how many people came.
{{{C=3*30+b}}}
{{{150=3*30+b}}}
{{{b=150-90}}}
{{{b=60}}}


Model Equation would be   {{{C=PQ+b}}}
or
{{{C=3Q+60}}}