Răspuns :
a-b=7
(a+b):(a-b)=13
(a+b):7=13
a+b=7x13
a+b=91
daca a-b=7,atunci a=b+7
deci inlocuim a in relatia a+b
b+b+7=91
2b+7=91
2b=91-7
2b=84
b=42
a=42+7
a=49
(a+b):(a-b)=13
(a+b):7=13
a+b=7x13
a+b=91
daca a-b=7,atunci a=b+7
deci inlocuim a in relatia a+b
b+b+7=91
2b+7=91
2b=91-7
2b=84
b=42
a=42+7
a=49
d=7
s:d=13
s:7=13
s=13x7
s=91
Deci s= suma=91
d=diferenta=7
a+b=91
a-b=7
a=b+7
b+7+b=91
2xb=91-7
2xb=84
b=84:2
b=42
a=b+7, adica
a=42+7=49
s:d=13
s:7=13
s=13x7
s=91
Deci s= suma=91
d=diferenta=7
a+b=91
a-b=7
a=b+7
b+7+b=91
2xb=91-7
2xb=84
b=84:2
b=42
a=b+7, adica
a=42+7=49