Respuesta :

P=2(w)+2(l)

length=x+4
width=x

2(x)+2(x+4)=20
use the distributive property

2x+2x+8=20
combine like terms

4x+8=20
subtract 8 from both sides

4x=12
divide both sides by 4 to isolate x

x=3

Length=x+4=3+4= 7
Width= 3