We'll solve this equation in order to find the score of the 4th test, which we denote with x.

. Solving it we find that x=63. And it is the final answer for this problem.
It would be 20, because 5 plus 4 is 9 and you can multiply 9 by 2 to get 18, 9 by 3 to get 27, and 9 by 4 to get 36, but you can't multiply anything by 9 to get to 20.
Answer:
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Step-by-step explanation: