Răspuns :
a+b=7,21
⇒a=2,17+b
⇒2,17+b+b=7,21
⇒2b=7,21-2,17
⇒2b=5,04
⇒b=2,52;
⇒a=2,17+2,52
⇒a=4,69;
⇒a=2,17+b
⇒2,17+b+b=7,21
⇒2b=7,21-2,17
⇒2b=5,04
⇒b=2,52;
⇒a=2,17+2,52
⇒a=4,69;
[tex]a+b=7,21 \\ a-b=2,17 \\ a+b+a-b=7,21+2,17 \\ 2a=9,38 \\ a=9,38:2=4,69 \\ b=7,21-4,69=2,52[/tex]