Answer:
a) 
b) 
c) Yes.
Step-by-step explanation:
We have that:

And we have $10 free of taxes.
Making x= number of tires to buy, then we have that the total cost of tires is:

So, what we pay for taxes is given by:

a) Then, according to the above, we can write down the total cost before the discount as:

b) And the total cost after discounts, is then given by:

c) If the discount is added first, then less tax will be paid because the amount on which it is paid is lower. If the discount is added later, then the taxes will have been taxed on a higher amount, so it does matter whether they are added first or later.
Number 21 is the first answer a.) 8
Answer: 1.25
Step-by-step explanation:
Given: A college-entrance exam is designed so that scores are normally distributed with a mean
= 500 and a standard deviation
= 100.
A z-score measures how many standard deviations a given measurement deviates from the mean.
Let Y be a random variable that denotes the scores in the exam.
Formula for z-score = 
Z-score = 
⇒ Z-score = 
⇒Z-score =1.25
Therefore , the required z-score = 1.25
X=48
Y=44
Because the triangles are congruent.
Answer:

Step-by-step explanation:
so first find the common denominator which is 162
so on 4/9 multiply 18 to denominater and numerator which makes it 72/162
next multiply 9 to numerator and denominator in 13/18 which makes it 117/162
so now add:

so now simplification.
189/162 can be reduced by 3
63/54 is our new answer. now we can reduce it by 9
7/6 is our new answer. now we must change it to a mixed number which is 
hope this helped!