You problem is you don't have any problem. You have a bunch of formulas for the perimeter and area of some shapes.
As for using the formulas, usually you're given all but one of the variables and you can solve for the remaining one.
Notice how the triangle result doesn't have area as a function of a, b and c. That's called Heron's formula and is usually not taught to secondary school students. I don't like to teach it either because Archimedes' Theorem is so much better:
The sides a,b,c and area S of a triangle satisfy

Quick answer: 68oF <<<<
A quick way to figure this out is to double the C temperature and add 30, just so you get an estimate.
F ~ 2*20 + 30 ~ 70oF
Now let's use the actual formula
F = 9/5 * C + 32
F = 9/5 * 20 + 32
F = 180/5 + 32
F = 36 + 32
F = 68o
68oC <<<<< answer.
Answer: n = 267
Step-by-step explanation: <u>Margin</u> <u>of</u> <u>Error</u> shows the percentage that will differ the result you get from the real population value or, in other words, is the range of values in a confidence interval.
It can be calculated as
margin of error = 
in which
z is z-score related to the confidence interval, which is this case is 1.96;
s is standard deviation;
n is the number in a sample;
So, the number of mice must be:
margin of error = 



n = 267
<u>For the margin of error with 95% confidence interval be 0.6, it is needed </u><u>267 mice</u><u>.</u>
Rounded up, it would be 7,540