1)
C-caiete
Ca-carti
3ca+4c=20lei
Ca=2c
Inlocuim in relatie:3x2c+4c=20lei
6c+4c=20lei
10c=20lei
C=20:10
C=2lei
Ca=2c => ca=2x2=4lei
2)
F-fete
B-baieti
P-panselute
15f+10b=420p
12f+10b=360p
.............................. (scadem termenii)
3f=60p
F=60:3
F=20p
15x20+10b=420p
300+10b=420p
10b=420-300
10b=120p
B=120:10
B=12p