Answer:
Amaya must get marks between 71 and 98 in order to get B grade
Explanation:
Amaya's test scores in algebra 1 are 78 and 91.
Let she got x marks in third test
The average all the three test must be 80-89
i.e.

Multiplying all sides by 3, we get
240≤ 78+91+x≤ 267
240≤ 169+x≤ 267
Subtracting all sides by 169, we get
71≤ x≤ 98
Hence, Amaya must get marks between 71 and 98 in order to get B grade