Question

What formula should I use for this?

Answer 1

If they're asking for the nth term, you should use n in your formula, ie.,

a(n) = 6000 * 0.5ⁿ

However, the first term is when n=1, so your formula should really be:

a(n) = 6000 * 0.5⁽ⁿ⁻¹⁾

Then the 8th term is 46.875