Answer
$y=24\cdot0.5^x$
Work Step by Step
Let $y=ab^x$.
Then our equations are: $48=ab^{-1}$ and $6=ab^2$.
If we divide the second equation by the first one we get: $0.125=b^3$, thus: $b=0.5$. Then $6=a\cdot(0.5)^2=0.25a\\a=24$.
Thus $y=24\cdot0.5^x$
