Răspuns :
x- nr de pagini
x-40x/100=120 / *100
100x-40x=12000
60x=12000
x=12000:60
x=200 pagini
x-40x/100=120 / *100
100x-40x=12000
60x=12000
x=12000:60
x=200 pagini
100la suta -40la suta=60la suta
Facem metoda de trei simpli
60.....120pag
100....x pag
60supra100=120supra x
X=100•120:60 =100•2=200pag