Goi so HS cua ca 3 lop 7A; 7B; 7C lan luot la a, b, c
=> \(\frac{a}{2}=\frac{b}{3}=\frac{c}{4}\)va a + b +c = 117
Ap dung tinh chat day ti so bang nhau, ta co :
\(\frac{a}{2}=\frac{b}{3}=\frac{c}{4}=\frac{a+b+c}{2+3+4}=\frac{117}{9}=13\)
=> a = 13 x 2 = 26 ( HS )
b = 13 x 3 = 39 ( HS )
c = 13 x 4 = 52 ( HS )
Vay so HS lop 7A la 26 HS.
so HS lop 7B la 39 HS.
so HS lop 7C la 52 HS.
( mik ko bit dung hay sai nua )