Fie x - nr. probleme rezolvate intr-o zi
ziua 1: x
ziua 2: x+3
ziua 3: x+6
ziua 4: x+9
ziua 5: x+12
ziua 6: x+15
ziua 7: x+18
x+x+3+x+6+x+9+x+12+x+15+x+18 = 77
7x+ 63=77
7x=14
x=2 probleme a rezolvat in prima zi
ziua 2: 2+3=5 probl.
ziua 3: 2+6=8 probl.
ziua 4: 2+9=11 probl.
ziua 5: 2+12=14 probl.
ziua 6: 2+15 =17 probl.
ziua 7: 2+18=20 probl.