a+(b+c)=462 timbre
Notam cu a pe -Ana
cu b pe - oana
cu c pe -mihai
a=17-b+19-c⇒ a=b+17+c+19
b+17+c+19+b+c=462
2b+36+2c=462
2b+2c=462-36
2b+2c=426/2
b+c=213
a+213=462
a=462-213
a=249
Verificare
a+b+c=462 timbre
249+213=462 timbre
2)
a+b+c=713
a=99+b
b=114-c
99+b+c+114+c=713/-b
99+c+114+c=713
99+2c+114=713
213+2c=713
2c=713-213
2c=500/2
c=250
b=c+114
b=250+114
b=364
a+364+250=713
a+614=713
a=713-614
a=99
Verificare
a+b+c=713
99+364+250=713
3)
Notam cu a -prima turma
Notam cu b-a doua turma
a=7*b=7b
a+b=1768
7b+b=1768
8b=1768/8
b=1768:8
b=221
a=7*221
a=1547
Verificare
a+b=1768
1547+221=1768
