When the particle is thrown , the initial velocity will be zero. So, using h = ut + 1/2gt^2, we get

h = 0 + 1/2*10*(5^2)

h = 125m

Now, the velocity after t = 5 seconds can be find using v^2 - u^2 = 2gh

So, v^2 = 2*10*125

v = 50 m/s

Now, this v is the u for the latter case, during 5th to 8th second.

So, H = 50*3 + 1/2*10*3*3

H = 195m

So, H-h = (195-125)m = 70m

Hope this helps.