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.
He is leaving 20% tip of the bill of $58
20% extra
So total amount = 100% + 20% = 120%
120% of 58
(120/100) * 58
1.2 * 58
= 69.6
So total amount Alexi needs to pay = $69.60
Answer:
The first term is 42.
Step-by-step explanation:
The common difference is 142 - 140 = 2 so we have
50th term = a1 + 2(50 -1) = 140 where a1 is the first term
a1 + 98 = 140
a1 = 140 - 98 = 42.
8.9
The equation for the grain size is expressed as the equality:
Nm(M/100)^2 = 2^(n-1)
where
Nm = number of grains per square inch at magnification M.
M = Magnification
n = ASTM grain size number
Let's solve for n, then substitute the known values and calculate.
Nm(M/100)^2 = 2^(n-1)
log(Nm(M/100)^2) = log(2^(n-1))
log(Nm) + 2*log(M/100) = (n-1) * log(2)
(log(Nm) + 2*log(M/100))/log(2) = n-1
(log(Nm) + 2*log(M/100))/log(2) + 1 = n
(log(33) + 2*log(270/100))/log(2) + 1 = n
(1.51851394 + 2*0.431363764)/0.301029996 + 1 = n
(1.51851394 + 0.862727528)/0.301029996 + 1 = n
2.381241468/0.301029996 + 1 = n
7.910312934 + 1 = n
8.910312934 = n
So the ASTM grain size number is 8.9
If you want to calculate the number of grains per square inch, you'd use the
same formula with M equal to 1. So:
Nm(M/100)^2 = 2^(n-1)
Nm(1/100)^2 = 2^(8.9-1)
Nm(1/10000) = 2^7.9
Nm(1/10000) = 238.8564458
Nm = 2388564.458
Or about 2,400,000 grains per square inch.