Răspuns :
a-b=60
b+13=a×2
a=60+b
b+13=(60+b)×2
b+13=120+2×b
2×b-b=120-13
b=107
a=107-60=47
a)/...../........60/
b)/...../...../+13
b=2a+13
a=60-13
a=47
b=47x2+13
b=94+13=107
verificare
107-47=60
b)/...../...../+13
b=2a+13
a=60-13
a=47
b=47x2+13
b=94+13=107
verificare
107-47=60