media artimetica ponderata este suma produselor numerelor cu ponderile lor impartita la suma ponderilor
map=(2·9+4·7+6·5+x·3)/(9+7+5+3)=(18+28+30+3x)/24=(76+3x)/24
4,1(6)=(416-41)/90=375/90=125/30=25/6
(76+3x)/24=25/6
76+3x=25·24/6
76+3x=25·4
3x=100-76
3x=24
x=8