We have been given that Alexis received an 85, 89, and 92 on three tests and we are asked to find out the minimum grade Alexis can score on the fourth test in order to have an average of at least 90.
Let x be marks Alexis can score on the fourth test.
Since we know average is sum of all the numbers divided by number of items. Now we can set our given information in the average formula to get the minimum numbers Alexis can score on the fourth test.
[tex]\frac{85+89+92+x}{4}=90[/tex]
[tex]85+89+92+x=4\cdot 90\\266+x=360\\x=360-266=94[/tex]
Therefore, the minimum grade Alexis can score on the fourth test is 94, in order to have an average of at least 90.
