In Latex, I used the arrray command to set up multiline equations:
Example: {lcr} means: 3 columns with indentations respectively left, center and right
\begin{array}{lcl} z & = & a \ f(x,y,z) & = & x + y + z \end{array}
To create a system: \begin {cases} equation\equation\end{cases}
To create a horizontal line: (for vertical adding)
\hline
To create the approximation symbol:
\approx{0.979 }
I couldn’t get the array function you used to work, but I found this one, and it seems to be working for me:
\begin{eqnarray}
x &=& 0\
y &=& \frac{1}{2}x+3\
y &=& \frac{1}{2}(\textcolor{blue}{0})+3\
y &=& 0+3\
y &=& 3\
\end{eqnarray}
Here are some other notations I’ve been using a lot:
fraction: \frac{numerator}{denominator}
text color: \textcolor{color}{text} (So, to have a red 3 in the text, you’d put “\textcolor{red}{3}”
?=: \stackrel{?}{=}
not equal: \neq
greater than or equal to: \geq
less than or equal to: \leq
I’ll add to the list as I think of more.
\begin{bmatrix} 3&4\4&-2\end{bmatrix}
\left ] \begin{array}{cc|c} 3&4&7\4&-2&5 \end{array}
\rightarrow
R_i \leftrightarrow r_j
\x rightarrow {After Gaussian elimination}
m \times n
not greater than: \ngtr
not less than: \nless
not less than or equal to: \nleq
not greater than or equal to: \ngeq
infinity: \infty
To make a table in LaTex for pressbooks:
\begin{array} {|r|c|} \hline \text{Point}& (2, 3) \ \hline \text{2nd Point} & (4, 5)\ \hline \end{array}
gives you:
In pressbooks in LaTex, using a $ in \text{$} will give a math processing error
a % sign will not display - needs to be coded as \text{%}
OK - I found out that if you put a \ in front of the $ or % it will print as part of the output. 
intersection: \cap (Example: “A \cap B”)
union: \cup (Example: “A \cup B”)
complement: ^{c} (Example: “A^{c}”)
To draw a numberline:
\begin{tikzpicture} [describe the line] (starting point) – (ending point) \end{tikzpicture}
so
\begin {tikzpicture} [thick, green] (0, 0)–(5, 0) \end{tikzpicture}
would draw a thick green horizontal line from (0, 0) to (0, 5)
If you want a vertical line, you would change the y-coordinates.
To label the points use the command \node [describe] at and a point {text}
so
\begin{tikzpicture} \node [above] at (0, 0) {point} \end{tikzpicture}
would show the word point above the place that is (0, 0)
To add braces around a set, use \ before each brace, but don’t put the space like I did here: \ { and \ } For some reason when I type it without the space between, the \ doesn’t show here.
empty set: \emptyset
bold letters for sets (for example, N for natural numbers): \mathbb{N}
~ : \sim
subset: \subset or \subseteq
element: \in
not an element: \notin
bold text: \textbf{}
italics: \textit{}
conjunction and: \land
disjunction or: \lor
iff: \leftandrightarrow