Answer:
[tex]90=\frac{261+x}{4}[/tex]
Step-by-step explanation:
Let x be the score on 4th test.
We have been given that Gavin's mean score on 3 math tests is 87.
Since we know that average is the sum divided by the count.
[tex]\text{Average}=\frac{\text{Total sum of all the numbers}}{\text{Number of items in the set}}[/tex]
Let us find sum of scores on 3 math tests by multiplying 87 by 3.
[tex]\text{Scores on 3 tests}=3* 87[/tex]
[tex]\text{Scores on 3 tests}=261[/tex]
Since Gavin needs the mean score on his 4 tests to be 90. This means score on 3 tests plus x divided by 4 will be equal to 90.
[tex]90=\frac{261+x}{4}[/tex]
Therefore, the equation [tex]90=\frac{261+x}{4}[/tex] can be solved to find the score that Gavin needs on his test to bring his mean score up to 90.
