Ty received test grades of 73%,82%,73%,77%, and 77%.

a) what grade would he need to make on the sixth test to get a "C" if a "C" is at least 75% but less than 80%?
b) Is it possible for Ty to get a B or better for his test average (at least 80%)?
ANSWERS:
To earn a C in the course, Ty must score at least a ( ??? )%
but less than (??? )% on the sixth test.

Please I need to fill the ???? in the parenthesis and solve letter "b"

6 answers

75 ≤ (73+82+73+77+77+b)/6 < 80

carry on
I don't understand.Please
let T equal the test grade

find the sum of 1st five tests ... call it S

6 * 75% = 450% ... 6 * 80% = 480%

a) 450% ≤ S + T < 480%

b) 480% ≤ S + T
75 ≤ (73+82+73+77+77+b)/6 < 80
75 ≤ (382+b)/6 < 80 , should be obvious what I did
450 ≤ 382+b < 480 , I multiplied everybody by 6, in the middle that canceled the 6 at the bottom
68 ≤ b ≤ 98, I subtracted 382 from everybody and I am done!

What does my last inequation tell you ?
a. 75 = (73+82+73+77+77+G)/6 < 80.
75 = (382 + G)/6 < 80,
Multiply by 6:
450 = (382+G) <480,
450-382 = G < 480 - 382,
68 = G < 98,
So he will need a grade(G) of at least 68 but less than 98.

b. (73+82+73+77+77+G)/6 = 80.
(382+G)/6 = 80.
G = ?
Yo what