notam cele doua lungimi a si b
a-lungime
b-latime
P=2(a+b)=220
(b+10)(a-20)=a*b <=>
<=>b(a-20)+10(a-20)=ab <=>
<=>ab-20b+10a-200=ab <=>
<=>-20b+10a-200=0 <=>
<=>10a=200+20b <=>
<=>a=20+2b
2(a+b)=220 => a+b=110 <=>
20+2b+b=110
3b=110-20=90=>b=30
a+b=110<=>a+30=110<=>a=80
