notam p=nr de probleme care trebuie să fie rezolvate
I zi⇒ 20%dinp=20p/100=p/5
aflăm restul p-p/5= (5p-p)/5= 4p/5
II zi⇒ 25%din rest= 25/100*4p/5=
=100p/500=100p/500=p/5
III zi⇒ 96 probleme
I zi+II zi+III zi= p, toate problemele
p/5+ p/5+ 96= p
p/5 + 480/5=5p/5 am adus la numitor comun 5
480= 5p-2p
p=480:3= 160
I zi⇒ p/5=160/5=32
II zi⇒p/5=160/5=32
total 160 probleme, prima zi 32, a doua zi 32, a treia zi 96