Using a system of equation, we have that:
a)
- x, which is the cost of on-site service.
- y, which is the cost of at-store service.
- z, which is the cost of by-mail service.
b)
The system is:



c)
The cost of one on-site repair service is of $90.
Item a:
The variables are:
- x, which is the cost of on-site service.
- y, which is the cost of at-store service.
- z, which is the cost of by-mail service.
Item b:
On-site service costs <u>3 times as much as at-store service</u>, thus:

By mail service costs <u>$10 less than at-store</u> service, thus:

Last week, the shop completed <u>15 services on-site, 40 services at-store, and 5 services by mail for total sales of $3100</u>, thus:

The system is:



Item c:
- The cost of one on-site repair service is x.
- First, replacing the first two equations into the third, we find y, and then with it we find x.






Then

The cost of one on-site repair service is of $90.
A similar problem is given at brainly.com/question/24823220
Answer:
See the second attachment for long division by hand. The first attachment shows the "work" I would usually do.
Step-by-step explanation:
In college math, you are generally expected to be able to make use of a scientific and/or graphing calculator. Division is one of the simpler operations these devices can perform.
If you are doing long division by hand, use the method you were taught in 3rd or 4th grade. The one shown is one of several different methods being taught now.
Let the year represents x axis and consumption represents y axis.
Since 2010 is the initial year, x=0
and 2013 is third year , so x=3
Co-ordinates are (0,8.938)(3,10.480)
Exponential formula is 
Putting the value of x in the above formula from 1st coordinate,

As
= 1
this gives a= 8.938
Now using the 2nd coordinate

putting the value of a in it we have

taking cube roots on both sides we get
b= 1.05448
Now putting the values of a and b in the exponential formula-

In the year 2028, x=28
so,

y= 39.474
Hence oil consumption per day in 2028 will be 39.474 million barrels.
Lets use 1 to solve this problem because it is easiest to show.
Multiply 1 by 1.3 for a 30% increase (1*1.3=1.3).
Then multiply 1.3 by .7 for a 30% decrease. (1.3*.7=.91)
Therefore the page had a 9% reduction from its original size or is 91% of its original size.
This is the correct answer to the problem