13/20 = x / 100
x = (13*100) / 20 = 65 % answer
Area(t) = Length * width
= L(t)*W(t)
=(t^2-sqrt(t))*(t^2-2t^(1/2))
..... Please check, w(t) does not seem to have been posted correctly
=t^4-3t^2*sqrt(t)+2t
Differentiate with respect to t:
Area'(t)
=4t^3-(15/2)t^(3/2)+2