Question

I don’t get how I get the numerators to be -8-3 here

Answer 1

First, notice that:

$\begin{gathered} 10=5\cdot2,\text{ } \\ \frac{2}{2}=1. \end{gathered}$

Therefore:

$-\frac{4}{5}=-\frac{4}{5}\cdot1=-\frac{4}{5}(\frac{2}{2})=-\frac{4\cdot2}{5\cdot2}=-\frac{8}{10}\text{.}$

That is how you go from -4/5 to -8/10.

Since -3/10 already has 10 as its denominator then it remains the same.

$-\frac{8}{10}-\frac{3}{10}=-\frac{11}{10}\text{.}$

Examples (negative numbers):

$\begin{gathered} -1-3=-(1+3)=-4, \\ 1-3=-2, \\ -1+3=2, \\ 1+3=4. \end{gathered}$$-1+3=3-1=2.$$\begin{gathered} -5+8=8-5=3, \\ -3+5=5-3=2. \end{gathered}$