Question 1207382
.


This is incorrect.


The "solution"/(suggestion) in the post by @josgarithmetic is incorrect, too.



The problem requires an accurate interpretation.


Such an interpretation and the correct solutions were given to this problem 
in this forum many years ago. See the links


https://www.algebra.com/algebra/homework/Average/Average.faq.question.209752.html


https://www.algebra.com/algebra/homework/word/misc/Miscellaneous_Word_Problems.faq.question.567475.html