Given:
Kaci earned scores of 78, 88, 87, and 91 on her first four science tests.
She has one more test to take and wants to get an average score of 80 or more on her tests.
Let the score of the final test = x
So, the average of the scores will be equal to or greater than 80
So, we have the following inequality
Solve for x:
So, the minimum score will be 56