__________________
x=1.4
y=-3.6
___________________
:)
        
             
        
        
        
Answer:= 261.905% increase
Solution:
Calculate percentage change 
from V1 = 21 to V2 = 76
(V2−V1)|V1|×100
(V2−V1)|V1|×100
=(76−21)|21|×100
=(76−21)|21|×100
=5521×100
=5521×100
=2.61905×100
=2.61905×100
=261.905%change
=261.905%change
=261.905%increase
        
             
        
        
        
Let's say side length is s. 
s*s = 500, so s = √500.
4 sides needed, total length thus 4*s.
4√500 ≈ 89.4
        
             
        
        
        
5x=3x+20
5x-3x=3x-3x+20
2x=20
2x/2=20/2
X=10   Hope this helped!
-Twix