Answer
$ a.\quad$Improper fraction:$\displaystyle \quad\frac{23}{5}.$
$ b.\quad$Mixed number:$\displaystyle \quad 4\frac{3}{5}$
Work Step by Step
Each object is divided into $5$ equal parts.
Each part represents $\displaystyle \frac{1}{5}$ of the object.
$23$ parts in all are shaded, or $\displaystyle \frac{23}{5}$.
As a mixed number, we have $4$ whole objects and $\displaystyle \frac{3}{5}$ of the last one...or, $4\displaystyle \frac{3}{5}$ .
( Dividing $23\div 5,$ quotient = $4$, remainder $3,$ so $\displaystyle \frac{23}{5}=4\frac{3}{5}$ )