Question 10
An and Binh play bowling with natural-number scores. $a$) An’s first two scores are $108$ and $125$; rounds $3$ and $4$ average $122$. What fifth score makes the five-round mean $120$? $b$) Binh’s first three average $113$, and his fourth and fifth scores are equal. Can his five-round mean be $120$? Explain.