Answer:
There are [tex]300\ boys[/tex] in 7th grade
Step-by-step explanation:
Let
x -----> the number of boys
y ----> the number of girls
we know that
[tex]\frac{y}{x}=\frac{3}{5}[/tex]
[tex]y=\frac{3}{5}x[/tex] ----> equation A
[tex]x+y=480[/tex] -----> equation B
Substitute equation A in equation B and solve for x
[tex]x+\frac{3}{5}x=480[/tex]
[tex]\frac{8}{5}x=480[/tex]
[tex]x=480*5/8[/tex]
[tex]x=300\ boys[/tex]
