Well first you substitute -3 for y and then subtract 12 from both sides of the equation and it should look like -15=-3x. Then divide 3 on both sides and you should end up getting 5=x.
Answer:
The value of the test statistic is 
Step-by-step explanation:
The null hypothesis is:
The alternate hypotesis is:
Our test statistic is:
In which X is the sample mean, 
is the null hypothesis value, 
is the standard deviation and n is the size of the sample.
In this problem:
So
The value of the test statistic is
2x -3y = 13
4x -y = -9
Multiply the second equation by -3 to make the coefficient of Y opposite the first equation.
4x -y = -9 x -3 = -12x + 3y = 27
Now add this to the first equation:
2x -12x = -10x
-3y +3y = 0
13 +27 = 40
Now you have :
-10x = 40
Divide each side by -10:
x = 40 / -10
x = -4
Now you have a value for x, replace that into the first equation and solve for y:
2(-4) - 3y = 13
-8 - 3y = 13
Add 8 to both sides:
-3y = 21
Divide both sides by -3:
y = 21/-3
y = -7
Now you have X = -4 and y = -7
(-4,-7)
Answer:
The cost of 4 medium pizzas:
4 (x - 3)
Step-by-step explanation:
#3
x = the cost of a large pizza
medium pizza costs $3 less than a large pizza. So it's x - 3
If 4 medium pizzas then it will be: 4 (x - 3)
