another student in the class had the following test scores:83,78,91,80,_?_ If this student has the same mean test scores as Susan and Samantha, what must have been their test score on the last test? Susan and Samantha had the mean test score of 84

84 * 5 = 420

The sum of 83,78,91,80 = 332

420 - 332 = 88 >> student's last score