ta goi so cay cua lop 7A 7B 7C lan luot la x , y, z
Ta co a/3 =y/4 =z/5 va a+b+c = 120
Ap dung day ti so bang nhau ta co :
a/3=b/4=z/5=a+b+c/3+4+5=120/12=10
a/3=10 => a=10.3=30
b/4=10 => b=10.4=40
c/5=10 =>c=10.5=50
vay so cay 7A trong duoc la 30 cay
7B =40
7C =50