notam cutiile A,B,C
A=20+B+C
B+20=C
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(B-10)*6=A+C
Rezolvare
inlocum C i prima si a treia ecuatie, si avem:
A=20+B+B+20
6B-60=A+B+20
Deci:
A-2B=40
5B-A=80
Le adunam:
A-2B+5B-A=120
3B=120
B=40 bomboane
C=B+20
C=60 bomboane
A=20+B+C
A=120 bomboane
PROBA
(40-10)*6= 120+60 ?
30*6= 180 √