1)x-lungimea drumului
30% din x= 30/100 *x= 3/10 *x= 3x/10 -prima data
x-3x/10= (10x-3x)/10= 7x/10 -restul
35% din 7x/10= 35/100 *7x/10= 7/20 *7x/10= 49x/200 -a doua oara
7x/10 -49x/200= (140x-49x)/200= 91x/200 -noul rest
91x/200=182
x=200*182/91
x=200*2
x=400km
2)Pr(AO) pe (AB)= OD
D∈AB
OD_|_AB
OD-h
A ΔAOB= b*h/2= OD*AB/2= 13*9/2= 117/2= 58,5
A ABCD=4*A ΔAOB =4* 58,5= 234
3)a= x² -12x +36= (x-6)²