Answer :

[tex]a_n=a_1\cdot q^{n-`1}\\\\a_1=2;\ q=0.5=\frac{1}{2}\\\\\\a_8=a_1\cdot q^{8-1}=a_1\cdot q^7\\\\a_8=2\cdot\left(\frac{1}{2}\right)^7=2\cdot\frac{1}{2^7}=2\cdot\frac{1}{128}=\frac{1}{64}\\\\\\Answer:a_8=\frac{1}{64}[/tex]