Answer:
Naomi will need to score at least 89% on her fourth test to have an average of 90% in her math class.
Explanation:
To find out what score Naomi needs to earn on her fourth test in order to have an average of 90%, we can set up an equation.
Let's denote the score on the fourth test as "x". Naomi has taken three tests, and their scores are 87%, 98%, and 86%. To find the average, we sum up all the scores and divide by the number of tests:
(87 + 98 + 86 + x) / 4 = 90
Now we can solve for x:
(87 + 98 + 86 + x) = 4 * 90
271 + x = 360
x = 360 - 271
x = 89
Naomi will need to score at least 89% on her fourth test to have an average of 90% in her math class.