this can help you
look at the image
r / 2 = h / 3
r = 2/3h
V = 1/3(pi)r^2h . Put r = 2/3h
V = 1/3(pi)(4/9)h^3 = 4(pi)/27h^3
dV/dt = 4(pi)/27(3h^2)dh/dt = 4/9(pi)(h^2)dh/dt
Plug in the numbers and solve for dh/dt at h = 0.8
dV/dt = 4/9(pi)(h^2)dh/dt = 1.396h^2dh/dt
dV/dt = 0.7, h = 0.8
0.7 = 1.39(.8^2)dh/dt
dh/dt = 0.78 meters / min
