The expression (x4)(x−8)x−10 is equivalent to xn. What is the value of n?

Answer 1

You probably meant:

xn = (x^4)(x−8)x−10
n = ( (x^4)(x−8)x−10 )/x

strange to have that multiplier of x hanging around at
the end of (x^4)(x-8)
I have a suspicion there are typos in your expression

Answer 2

I suspect the problem was
(x^4)(x^-8)(x^-10) = x^(4-8-10) = x^-14
so n = -14