Are the directions asking you to solve these ?
Answer: 
Step-by-step explanation:
Given
Propane produced heat energy of 
The volume of the tank is 
The energy produced by this propane tank is

First, make up some variables to represent the number of Girls and Boys in the choir.
B = number of boys
G = number of girls
You know that there are 4 times as many girls in the choir as boys. Therefore, the equation you can write is:

If you cross-multiply, then you get the simplified equation:
G = 4B
Intuitively this makes sense since if you multiplied the number of boys in the class by 4, that would be equal to the number of girls you have.
Now, we know that the total class size is 60. So girls plus boys equals 60:
G+B = 60
To solve the equation, replace the G in this equation with the replacement you found before, 4B.
G + B = 60 -->
4B + B = 60 -->
5B = 60 -->
B = 12
However, you are trying to find the number of girls, so plug the answer back into your equation.
G + B = 60 -->
G + 12 = 60 -->
G + 12 -12 = 60 - 12 -->
G = 48
The number of girls you have is 48.
Given:
Point B has coordinates (4,1).
The x-coordinate of point A is -4.
The distance between point A and point B is 10 units.
To find:
The possible coordinates of point A.
Solution:
Let the y-coordinate of point A be y. Then the two points are A(-4,y) and B(4,1).
Distance formula:

The distance between point A and point B is 10 units.

Taking square on both sides, we get



Taking square root on both sides, we get



and 
and 
Therefore, the possible coordinates of point A are either (-4,-5) or (-4,7).