They must have the same variable with the same exponent. The coefficient doesn't matter much.
The answer is AA Similarity
You put the 15x + 100 on the angle CEB instead of CED. If you put it in the right spot, it should work out fine since they are vertical angles.
I attached the document with the answers and work with the formulas. Since the formulas and fractions don't work very well with this site (especially the pi symbol, they should fix that).
:)
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