Step-by-step explanation:
We have
87+86+x
T is the total scores
n is number of tests done = 3
T/n is greater than or equal to 90
To get minimum test
T/n = 90
T = 90*n
= 90n
We solve for x
Remember n = 3
90x3 = 270
270 = 87+86+x
270 = 173+x
X = 270-173
X = 97
1.
X = 97
2.
You didn't add a value in your part b question. I used 80 though.
T/n < 80
T<80n
80x3= 240
T<240
87+86+x<240
X<240-173
X<67
X has to be less than 67 so we conclude that if x <=67 b grade will be lost.
A =

p = principal amount (the initial amount you borrow or deposit)
r = annual rate of interest (as a decimal)
t = number of years the amount is deposited or borrowed for.
A = amount of money accumulated after n years, including interest.
n = number of times the interest is compounded per year

$2,697.20
B: -3.5,-2.7,-2.69,-2.66,-1.49
The function rule I will be using is this:

Four ordered pairs that could represent this linear function are:
(0, 5)
(1, 7)
(2, 9)
(3, 11)