Answer:
A sample of 179 is needed.
Step-by-step explanation:
We have that to find our
level, that is the subtraction of 1 by the confidence interval divided by 2. So:

Now, we have to find z in the Ztable as such z has a pvalue of
.
That is z with a pvalue of
, so Z = 1.44.
Now, find the margin of error M as such

In which
is the standard deviation of the population and n is the size of the sample.
A previous study found that for an average family the variance is 1.69 gallon?
This means that 
If they are using a 85% level of confidence, how large of a sample is required to estimate the mean usage of water?
A sample of n is needed, and n is found for M = 0.14. So






Rounding up
A sample of 179 is needed.
Step-by-step explanation:
The Midpoint Formula works exactly the same way. If you need to find the point that is exactly halfway between two given points, just average the x-values and the y-values.
First you have to find the slope with the equation y2 - y1 / x2 - x1 , then once you have found the slope (slope = -2) you simply plug it into the point slope formula. y-0 = -2(x-5) solving it algebraically you should arrive at Y=-2x+10. (the 5 and 0 were plugged in are two of the X and Y points of the line which is why we plugged them into the X and Y values of the equation)
No one can help you if you dont show us the work my dude. But the was to convert them is say you have 1/4 that is 25% of a whole. Sorry i couldnt help more repost the question with a link and people can help then.
Slope intercept form is y=mx+b.
Y and x stay.
M is your slope.
B is your y-intercept.
Hope that this helps!