Question 140336
Let {{{g}}}= the number of girls
The number of boys ={{{7700 - g}}} 
{{{(7700 - g) / 7700 = 4/11}}}
Multiply both sides by {{{11*7700}}}
{{{11*(7700 - g) = 7700*4}}}
{{{84700 - 11g = 30800}}}
{{{-11g = -53900}}}
{{{g = 4900}}}
There are 4,900 girls in Surf City
check answer
{{{7700 - g = 7700 - 4900}}}
number of boys = {{{2800}}}
{{{2800 / 7700 = 4/11}}}
multiply both sides by {{{11*7700}}}
{{{11*2800 = 4*7700}}}
{{{30800 = 30800}}}
OK