Urgetnt - Revised ETA's

[C-N]

dry textbooks

and this could be the dry, direct answer: (again without calculus)

d=300nm (assuming thats ground distance you have given)
v=260nm/hr (knots)

with that v you'll arrive 1hr 9.2mins
but you want it delayed 8mins.

Hence, new ETA 1hr 17.2mins or 1.28667hrs

let x be the whole distance where v=200nm/hr in order to meet your revised ETA:

x/200 = 1.286667
x=257.3334nm (ground distance)

or 9.8461mins from now, so act quickly.

challenge: post a one liner differential calculus solution