x - the number of boys
y - the number of girls
The ratio of boys to girls is 5:7.
[tex]\frac{x}{y}=\frac{5}{7} \\
7x=5y \\
x=\frac{5}{7}y[/tex]
There are 36 children in the class.
[tex]x+y=36 \\
x=36-y \\ \\
x=x \\
\frac{5}{7}y=36-y \\
\frac{5}{7}y+y=36 \\
\frac{5}{7}+\frac{7}{7}y=36 \\
\frac{12}{7}y=36 \\
y=36 \times \frac{7}{12} \\
y=3 \times 7 \\
y=21 \\ \\
x=36-y=15 \\ \\
21-15=6[/tex]
There are 6 more girls than boys in the class.
