Question

Going into the final exam which will count as two-thirds of the final grade, Mike has test scores of 86,80,84,and 90. What score does he need on the final to earn an average score of 80?

Is this right:
(86+80+84+90)/4 = 80
2/3x(85)= 80

or ((86+80+84+90+(2/3x))/5 = 80

Answer 1

the mean of the four test scores is worth 1/3 of his grade while his final is worth 2/3 of his grade

here's how to set it up:
(1/3)[(86+80+84+90)/4]+(2/3)x=80