1.
x=nr pagini carte
x=2x/7+80
7x=2x+560
5x=560
x=112 pagini
2.
a=nr baieti
a+25=nr elevi
a/a+25=3/8
8a=3a+75
5a=75
a=15 baieti
15+25=40 elevi
3.
x=suma de bani
2x/3=suma ptr carti
x-2x/3=x/3 =rest
x/3 *1/5=x/15 =suma ptr pix
2x/3+x/15+20=x
10x+x+300=15x
4x=300
x=75 lei a avut Adrian
75x2/3=50 lei ptr carti
(75-50)*1/5=25*1/5=5 lei ptr pix