To determine which of the expressions are undefined and plot the remaining quotients on a number line, we need to evaluate each expression.
We have: $$\begin{array}{rl}\frac{x}{4}{\textstyle \phantom{\rule{1em}{0ex}}}& \text{(Quotient, where}x\text{is any number)}\\ \\ \frac{-21}{-7}& =3{\textstyle \phantom{\rule{1em}{0ex}}}\text{(Quotient of two negative numbers)}\\ \\ -4\xf70& \text{is undefined}\\ \\ -25\xf7(-5)& =5{\textstyle \phantom{\rule{1em}{0ex}}}\text{(Quotient of two negative numbers)}\\ \\ \frac{36}{-9}& =-4{\textstyle \phantom{\rule{1em}{0ex}}}\text{(Quotient of a positive and a negative number)}\\ \\ \frac{9}{0}& \text{is undefined}\\ \\ 0\xf7x& =0{\textstyle \phantom{\rule{1em}{0ex}}}\text{(Quotient, where}x\text{is any non-zero number)}\end{array}$${:[(x)/(4)quad(Quotient, where x" is any number)"],[],[(-21)/(-7)=3quad(Quotient of two negative numbers)],[],[-4-:0" is undefined"],[],[-25-:(-5)=5quad(Quotient of two negative numbers)],[],[(36)/(-9)=-4quad(Quotient of a positive and a negative number)],[],[(9)/(0)" is undefined"],[],[0-:x=0quad(Quotient, where x" is any non-zero number)"]:}
Therefore, the expressions that are undefined are $-4\xf70$-4-:0 and $\frac{9}{0}$(9)/(0). The remaining quotients are:

$$3,5,-4,0.$$3,5,-4,0.

We can plot these on a number line (not to scale) as follows:

The circle indicates that the endpoint is not included in the interval. So, for example, the quotient $-4$-4 is between the endpoints $-4$-4 and $0$0, but $-4$-4 is not included.