Step-by-step explanation:

Cost of company A=monthlyfee+text=20+0.03t where t=number of texts
A=20+0.03t
company b is monthlyfee+texts=5+0.07t
B=5+0.07t
1.
c=20+0.03t
c=5+0.07t
using c for cost is confusing because we can't tell which is for which company
2.
equal, means the costs are equal so
20+0.03t=5+0.07t
minus 5 from both sides
15+0.03t=0.07t
minus 0.03t from both sides
15=0.04t
divide both sides by 0.04
375=t
the answer is 375 texts
Answer:
-4 =x
Step-by-step explanation:
5x+8=3x
Subtract 5x from each side
5x-5x+8=3x-5x
8 = -2x
Divide by -2
8/-2 = -2x/-2
-4 =x
"inversely proportional," please.
z = k/x
When x is 3, z = 6; find k: 6 = k/3, or k = 18.
Then z = 18/x. When x = 12, z = 18/12 = 2/3 (answer)
Answer:


Since the calculated values is lower than the critical value we have enough evidence to reject the null hypothesis at the significance level of 2.5% and we can say that the true mean is lower than 36 years old
Step-by-step explanation:
Data given
represent the sample mean
represent the sample standard deviation
sample size
represent the value that we want to test
represent the significance level for the hypothesis test.
t would represent the statistic (variable of interest)
represent the p value for the test (variable of interest)
System of hypothesis
We need to conduct a hypothesis in order to check if the true mean is less than 36 years old, the system of hypothesis would be:
Null hypothesis:
Alternative hypothesis:
The statistic is given by:
(1)
And replacing we got:
Now we can calculate the critical value but first we need to find the degreed of freedom:

So we need to find a critical value in the t distribution with df =21 who accumulates 0.025 of the area in the left and we got:

Since the calculated values is lower than the critical value we have enough evidence to reject the null hypothesis at the significance level of 2.5% and we can say that the true mean is lower than 36 years old