Question

Cate timbre are Cezara in fiecare din cele patru clasoare ale sala daca:
in total are 987 timbre romanesti si straine;
in al treilea clasor are 120 de timbre;
in primul si al doilea clasor are 502;
in al doilea si al patrulea clasor are 679.

Answer 1

notam clasoarele cu a,b,c si d
a+b=502
c=120
b+d=679
a+b+c+d=987
a+b+120+d=987
a+b+d=987-120
a+b+d=867
502+d=867
d=867-502
d=365
de la capat
b+d=679
b+365=679
b=679-365
b=314
de la capat
a+b=502
a+314=502
a=502-314
a=188

verificare
188+314+120+365=987
CORECT