Question 85724
Let a=adults, c=children
{{{11a+10c=246}}}money made from adult's and children's tickets
{{{a+c=23}}} number of people
{{{a=23-c}}} solve for any variable, in this case a
{{{11*highlight((23-c))+10c=246}}}plug in value of a in terms of c
{{{253-11c+10c=246}}}Distribute
{{{253-c=246}}}Simplify
{{{-c=-7}}}Isolate c
{{{c=7}}}Negate to make c a positive number 
So the number of children that attended is 7

So the answer is C)