Question 411182
I can say:
(children)/(adults) = 7/3
I can also say:
(children)/(children + adults) = 7/(7 +3)
and
(adults)/(children + adults) =  3/(7 + 3)
-------------------
I'm told that children + adults = 820
therefore
{{{c / 820 = 7/10}}}
and
{{{a / 820 = 3/10}}}
---------------
{{{c = (7/10)*820}}}
{{{c= 574}}}
and
{{{a = (3/10)*820}}}
{{{a = 246}}}
There are 574 children
check answer:
{{{a + c = 246 + 574}}}
{{{a + c = 820}}}
OK