Question: Differential Equations help pt.2

Hi! so im working on the next problems now:

Show that dV/dt = -k * V^(2/3) given that k = 0.4836 and t is measured in minutes if the original volume of the capsule is 300 ml, how long will it take the capsule to lose half its volume?

Im doing this on maple right now and see you if guys can spot my problem or my syntax:

1. eq1 := diff(y(t), t) = -k*y(t)^(2/3)

2. dsolve(eq1, y(t)) which gives me an equation

3. dsolve({eq1, y(0) = 300}, y(t)) here i set the equation to equal to 300 to find my C

4. solve(subs(k = .4836, Y(t)), t) here i tried finding the time needed to lose half its volume but its giving me a set of numbers

So with oliver's help i was able to understand my syntax problems =D now on part 2:

Assuming the same size capsule as in question 2, suppose that the change in volume of the second capsule were instead directly porportional to its volume, and after 2 minutes, only 75 ml of the capsule's volume still remained. How long would it taje this capsule to lose half its volume.

So i went ahead and used the same technique as i need in number one and i ended up with approx. 7 minutes. But this wasnt directly porportional to the volume of the capsule. I tried figuring out what the equation would become but the only one situation i could think of was dV / dx = k*V but that didnt look right to me. In class, we didnt do much of these kinds of situations so any help in figuring the new equation would be awesome!

From there two more questions are asked asking when will the two capsules start to dissolve at the same time and when will the difference in their volumes be the greatest and the rate of change of the volumes. But for now, part 2 is kinda confusing me, after doing part 1 i know how to solve for the time, but in part 2 a different equation is needed

All Help is again grealty appreciated!

Thanks!