Changing from negative to positive
Answer: That would be 15ft
The midpoint of 85 and 90 is 87
For this case we have:
Cost of manufactures of T-shirts 
where x represents the number of T-shirts
Part A:
Substituting
in the total cost equation you have to:

Thus, the cost of 8 shirts will be 
Part B:
If
then

Thus, the cost of 12 shirts will be 
Answer:

Answer:
3 1/20
Step-by-step explanation:
First, we will convert the mixed numbers into improper fractions...
9 3/10 (9*10=90+3=93) so the improper fraction is 93/10
5 3/4 (5*4=20+3=23) therefore the improper fraction is 23/4
We then want to make the denominator the same...
93/10 (*4) = 372/40
23/4 (*10) = 230/40
We then put it into the question...
372/40 - 230/40 = 142/40
Lastly, we now need to turn this into a mixed number...
142/40=3.55 so the answer is 3 2/40
3 2/40 in it's simplest form is 3 1/20
Hope this helps!