Answer: 10
2AX=BD
2(3y-5)=5y
6y-10=5y
add 10 to each side 6y+10-10=5y+10
6y=5y+10
subtract 5y from each side 6y-5y=5y-5y+10
6y-5y=y
y=10
Well first do 20 children minus 8 girls to find how many boys there are:
20-8=16
So there are 16 boys. Therefore we can write the ratio of girls to boys as:
8/16
Then we can simplify this ratio by dividing it by 8 to get:
1/2
So the answer is the ratio of girls to boys in the group in simplest form is 1/2.
That's pretty much a tricky question though
The cotangent function is defined as the ratio between cosine and sine of a given angle, i.e.

Since you can't have zero at the denominator, the cotangent function is not defined when the sine is zero.
Let's look at your option:
, so the cotangent is defined here
, so the cotangent is not defined here
, so the cotangent is defined here
, so the cotangent is defined here
First is 0.06 and second 0.2