`4)`
$\text{($\dfrac{4}{1.3}$ + $\dfrac{4}{3.5}$ + ... + $\dfrac{4}{97.99}$ + $\dfrac{2}{99}$) : $\dfrac{1}{$2^{-3}$}$}$
$\text{= 2($\dfrac{2}{1.3}$ + $\dfrac{2}{3.5}$ + ... + $\dfrac{2}{97.99}$ + $\dfrac{1}{99}$) : $\dfrac{1}{0,125}$}$
`= 2(1 - 1/3 + 1/3 - 1/5 + ... + 1/97 - 1/99 + 1/99) : 8`
`= 2.1 : 8`
`= 2/8`