Question 653275
Great question!  Though the student should aim higher than a 76% :)

If his average on the final exam counts for 1/3 of his overall grade, then the average of all the test scores he's already taken will count as 2/3 of his grade.  "of" in math means to multiply.  So:

Let's first find his test average:

(72+83+65+73+62)/5 = 71

His test averaage has been a 71.

So, 2/3 of 71 = (2/3)(71) = 47.33

Now set up the problem:

47.33 + (1/3)(x) = 76  (x stands for his grade on the final)

(1/3)(x) = 28.66  (subtracted 47.33 from both sides)
x = 86 (multiplied both sides by 3 to get rid of 1/3

He needs an 86% on the final.