Question 684202
x + y = 49
x is boys, y is girls
y = {{{2/5}}}x
...
Substitute
x + {{{2/5}}}x = 49
Multiply the entire equation by 5 to remove the fraction
5x + 2x = 245
7x = 245
{{{highlight_green(x = 35)}}} boys
y = 49 - 35 = {{{highlight_green(y=14)}}} girls
.....................
Have more questions? 
Email: HomeworkHelpers@readingboosters.com
Delighted to help.
-Reading Boosters
Website: www.MyHomeworkAnswers.com 
Wanting for others what we want for ourselves.