Răspuns :
a+b=77
b-a=11
2b=77+11
2b=88
b=88:2
b=44
a+44=77
a=77-44
a=33
PROBA
a+b=33+44=77
b-a=44-33=11
b-a=11
2b=77+11
2b=88
b=88:2
b=44
a+44=77
a=77-44
a=33
PROBA
a+b=33+44=77
b-a=44-33=11