We start to solve this by looking for the formula that let us calculate an average value, this formula would be:
where Save is the average score and s is the score of each exam, Since we know the value of the score Save and 4 of the exams we can replace them in the formula, like this:
And we can solve for s5, which is the score that we need to find, like this:
Then, Pedro must have a 55 score on the fifth test
