f=Foot
A=Area of the rectangular invitation card
L=Length of the rectangular invitation card
P=Perimeter
W=Width of the rectangular invitation card
------------------------
A=3/10f²
L=4/5f
-------------------------
A=L*W=3/10f²
So...
4/5f*W=3/10f²
So...
W=(3/10f²)/(4/5f)
So...
W=3/8f
--------------------------
Now:
P=2W+2L
=2(3/8f)+2(4/5f)
=3/4f+8/5f
=15/20f+32/20f
=47/20f
=(40/20+7/20)f
=(2+7/20)f
=2.35f
