Answer:
76
Step-by-step explanation:
Formula
[tex]\sf Average=\dfrac{\textsf{sum of all the numbers}}{\textsf{amount of numbers}}[/tex]
Given values:
- First three test scores: 84, 78 and 82
- Total number of tests = 4
- Average score for all four tests = 80
Let x be the score of the fourth test.
To find the score of the fourth test, substitute the given values into the formula and solve for x:
[tex]\begin{aligned} \sf Average & =\dfrac{\textsf{sum of all the numbers}}{\textsf{amount of numbers}}\\\\\implies \sf 80 & = \sf \dfrac{84+78+82+x}{4}\\\sf 80 & = \sf \dfrac{244+x}{4}\\\sf 80 \cdot 4 & = \sf 244 + x \\\sf 320 & = \sf 244 + x\\\implies \sf x & = \sf 320 - 244\\& = \sf 76\end{aligned}[/tex]
Therefore, John scored 76 on his fourth test.
