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
The most appropriate choice for similarity of triangles will be given by -
Speed of tip of the shadow of woman = 6 ft/s
What are similar triangles?
Two triangles are said to be similar, if the corrosponding angles of the triangles are same and the corrosponding sides of the triangles are in the same ratio.
Here,
The diagram has been attached here
Let the distance of woman from the pole be x ft and the distance of tip of the shadow to the pole be y ft.
Height of street light = 18 ft
Height of woman = 6ft
The two triangles are similar [As height of woman is parallel to the height of pole]

To find the speed, we have to differentiate both sides with respect to time 't'

Speed of tip of her shadow = 6 ft
To learn more about similarity of triangles, refer to the link-
brainly.com/question/14285697
#SPJ4
It would be a right angle
The answer is E histogram
X + 4y = 3 x = -4y + 3
2x - 3y = 17
2(-4y + 3) - 3y = 17
-8y + 6 - 3y = 17
-11y + 6 = 17
-11y = 11
y = -1
x = -4(-1) + 3
x = 4 + 3
x = 7
(7, -1) is your answer