Răspuns :
a+b=7,21 a=7,21-b a=7,21-b a=7,21-b
a-b=2,17 <=> 7,21-b-b=2,17 <=> 7,21-2b=2,17<=> 2b=7,21-2,17 <=>
a=7,21-b a=7,21-b a=7,21-b a=7,21-2,52 a=4,69
2b=5,04 <=> b=5,04/2 <=> b=2,52 <=> b=2,52 <=> b=2,52
a-b=2,17 <=> 7,21-b-b=2,17 <=> 7,21-2b=2,17<=> 2b=7,21-2,17 <=>
a=7,21-b a=7,21-b a=7,21-b a=7,21-2,52 a=4,69
2b=5,04 <=> b=5,04/2 <=> b=2,52 <=> b=2,52 <=> b=2,52