40% au luat note peste 7 adica 12 elevi
daca 40%=12 elevi atunci + inca 40% sunt 24 de elevi si + inca 20%(adica 6 elevi) sunt 30 de elevi in clasa
10%=3elevi
20%=6elevi
30%=9elevi
calculam media:
(3*10)+(3*9)+(6*8)+(9*7)+(6*8)+(3*5)=231
231:30=7,7(media totala)