If an integer is chosen between 1 and 50 inclusive, you have 50 numbers total to deal with, so 50 is in the denominator of our ratio (fraction). All the numbers divisible by 3 in that interval total 16 numbers. So the ratio would be 16/50 for a percentage of 32%
Well we know that 10 and 3/4 is equivalent to 10.75. If we divide the meat into 8 equal packages we have to divide 10.75 by 8. Dividing 10.75 by 8 gives us 1.34375 pounds of meat per package. If we take that, and multiply it by our given value of $3.40 per pound, we end up getting $4.57 a package.
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.