By substitution, the solution of the system of equations, 4x + 2y = 7 and y = 5x, is (1/2 , 5/2).
A system of linear equations is a set of two or more equations which includes common variables. To solve system of equations, we must find the value of the unknown variables used in the equations that must satisfy both equations.
There are three methods that can be used to solve system of linear equations.
1. Elimination
2. Substitution
3. Graphing
Using substitution method, given two linear equations in x and y,
4x + 2y = 7 (equation 1)
y = 5x (equation 2)
Since the second equation is already expressed in y in terms of x, substitute the second equation to the first equation.
4x + 2y = 7 (equation 1)
4x + 2(5x) = 7
4x + 10x = 7
Combining all terms containing the variable x on one side and the constants on the other side of the equality, and solving for x.
4x + 10x = 7
14x = 7
x = 1/2
Substitute the value of x in the second equation and solve for y.
y = 5x
y = 5(1/2)
y = 5/2
Hence, the solution of the given system of equations is (1/2 , 5/2).
To learn more about solving systems of equations: brainly.com/question/25869125
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The answer is C you have to convert 20 % in a decimal 0.2
Answer:
The 90% confidence interval is (0.1897, 0.2285).
Step-by-step explanation:
In a sample with a number n of people surveyed with a probability of a success of
, and a confidence interval
, we have the following confidence interval of proportions.

In which
Z is the zscore that has a pvalue of 
For this problem, we have that:
From a July 2019 survey of 1186 randomly selected Americans ages 18-29, it was discovered that 248 of them vaped (used an e-cigarette) in the past week. This means that 
Construct a 90% confidence interval to estimate the population proportion of Americans age 18-29 who vaped in the past week.
So
, z is the value of Z that has a pvalue of
, so
.
The lower limit of this interval is:

The upper limit of this interval is:

The 90% confidence interval is (0.1897, 0.2285).
Answer: 13. -68
14. 36
15. -36
16. -3
17. 10
18. -4
19. 1310 ft
20. 330 ft
Step-by-step explanation:
13. 34*(-2)=-68
14. -9*(-4)=
-(9*(-4))=
-(-36)=36
15. 12*(-3)=-36
16. -12/4=-3
17. -20/(-2)=
20/2=10
18. 200/(-50)=-4
19. -1640*(-1)-(-330*(-1))=
1640-(-330*(-1))=
1640-330=1310 ft
20. -990*(-1)-(-660*(-1))=
990-(-660*(-1))=
990-660=330 ft