Answer:
(-1, -5)
Step-by-step explanation:

1. We must calculate x, for that we must substitute y, so we have:
5x=9x+4
2. Now we solve the equation.
5x-9x=4
-4x=4
x=-1
3. Now we must calculate y
y=5x
y=5(-1)
y=-5
And the answer is (-1, -5)
Answer:
Infinite solutions
Step-by-step explanation:
Given is a system of equations.
-3x+y=10
-6x+2y=20
Equation I when multiplied by 2, gives as
-6x+2y =20 which is the same as equation 2 given.
This gives the two lines are not intersecting nor parallel. But the two lines are coincident with each other.
Hence each point on the line is solution.
Infinite solutions.
Let us try to solve and verify this
BY substitutition we have y = 3x+10, substitute in II
-6x+2(3x+10) =20
Or -6x+6x+20=20
20=20 Thus for any x, this becomes true.
Hence infinite solutions.
Answer:
The first student, with 20 measurements, will have the more precise interval due to the larger sample size.
Step-by-step explanation:
Margin of error of a confidence interval:
The margin of error of a confidence interval has the following format:

In which z is related to the confidence level, s to the standard deviation and n to the sample size.
The margin of error is inversely proportional to the square root of the sample size, which means that a larger sample will lead to a lower margin of error, that is, to a more precise interval.
In this question:
One student will use 5 measurements, other 20. The first student, with 20 measurements, will have the more precise interval due to the larger sample size.
where is the figures to solve.
First let's set up our equation properly.
0=5c-15
Now we can get the variable and constant alone by adding 15 to both sides.
5c=15
Next we divide 5 to both sides to get our variable c alone.
c=3