From the given
a = 2x 
r = 8 
b = 1/x 
m = r  1 = 7 
n = 10 

$r^\text{th} ~ \text{term} = (nCm)(a^{n  m})(b^m)$
$8^\text{th} ~ \text{term} = (10C7)(2x)^{10  7} \cdot \left( \dfrac{1}{x} \right)^7$
$8^\text{th} ~ \text{term} = (120)(2^3)(1)^7 \cdot \dfrac{x^3}{x^7}$
$8^\text{th} ~ \text{term} = \dfrac{960}{x^4}$
Coefficient of the 8^{th} term = 960 ← answer