Answer:

where
is the number of laptops, and
is the year.
in 2017: 
Step-by-step explanation:
I will define the variable
as the number of years that passed since 2007.
Since the school buys 20 lapts each year, after a number
of years, the school will have
more laptops.
and thus, since the school starts with 31 laptops, the equation to model this situation is

where
is the number of laptops.
since x is the number of years that have passed since 2007, it can be represented like this:

where
can be any year, so the equation to model the situation using the year:

and this way we can find the number of laptos at the end of 2017:

and


Answer: Choice C) -11
-----------------------------------
Explanation:
The first equation given is y = 3 - 1/2x
In other words, y is the same as 3 - 1/2x.
We can replace y in the second equation with 3 - 1/2x
This is known as substitution (think of a substitute teacher who is a temporary replacement for your teacher)
Doing this leads to...
3x+4y = 1
3x+4*y = 1
3x+4*( y ) = 1
3x+4*( 3 - 1/2x ) = 1 <<--- y has been replaced with 3-1/2x
3x+4*(3) +4*(-1/2x) = 1
3x+12-2x = 1
3x-2x+12 = 1
x+12 = 1
x+12-12 = 1-12 <<-- subtracting 12 from both sides
x = -11
Which is why the answer is choice C) -11
Answer:
Solution By Gauss jordan elimination method
x = 3, y = 2 and z = 4
The answer to your question is TRUE
To find the answer, set up an equation:

Using this set up we can cross out the units that are on opposite sides of the proportion such as miles and hours, leaving us with the desired units of meters and seconds. Then calculate m/s by multiplying 45 by 1000 meters and then dividing that value by 3600 seconds.
The resulting answer is 45mph = 12.5 m/s