"pre" tags will put the symbols in the positions you want. Left arrow, pre, right arrow, and then your content of symbols, and then left arrow, forward slash, pre, right arrow.
L M
__________3x-33________/______/___________
/ /
/ / 2x+26
You seem to want to label the two opposite exterior angles with expressions, so...
L M
3x-33 / /
_______________________/______/___________
/ /
/ / 2x+26
The vertical angle of each of them is also that same value, so...., , if you want L and M to be parallel.
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Find the hyperlink that says, Show Source or View Source. You will be able to see the code for this.