Related Rates

$y=\sqrt x\\ y=x^{0.5}\\ \frac{dy}{dt}=0.5x^{-0.5}\cdot \frac{dx}{dt}\\ \frac{dy}{dt}=\frac{1}{2\sqrt x}\cdot \frac{dx}{dt}\\ When\;\;x=4\\ \frac{dy}{dt}=\frac{1}{4}\cdot \frac{dx}{dt}\\$

I could have done that more simply . Oh well, too bad.

a)      

$Since\;\; \frac{dx}{dt}=3\;\;then\\ \frac{dy}{dt}=\frac{3}{4}\\~\\ \text {that is when x=4}$

You can do the other one.  :)