Răspuns :
A=P:5
A+25=P-75
dar A=P:5
P:5+25=P-75
75+25=P-P:5
100=P-P:5 aducem la acelasi numitor
500=5P-P
500=4P
P=500:4
P=125
A=P:5=125:5
A=25
deci Alina are 25 de lei, Petre are 125 lei
verificare
A+25=P-75 25+25=125-75 50=50 se verifica
A+25=P-75
dar A=P:5
P:5+25=P-75
75+25=P-P:5
100=P-P:5 aducem la acelasi numitor
500=5P-P
500=4P
P=500:4
P=125
A=P:5=125:5
A=25
deci Alina are 25 de lei, Petre are 125 lei
verificare
A+25=P-75 25+25=125-75 50=50 se verifica