Notam
X = nr problemelor rezolvate corect
20-X = nr problemelor rezolvate gresit
10×X-2×(20-X) = 176
10×X-40+2×X= 176
12×X = 176+40
12×X = 216
X = 216:12
X = 18 ( probleme rezolvate corect)
20-X = 20-18 = 2 (probleme rezolvate gresit)
Verficare:
18+2 = 20
10×18-2×2 = 180-4 = 176