Question

In a group of 80 children there are three times as many boys as girls how many girls are there ?

Answer 1

If I assume the number of girls is x, then the number of boys will be 3x
We know there are 80 children is 80, therefore
x+3x=80
4x=80
x=20
There are 20 girls.

Answer 2

Hi there! ~

Okay, so lets say that 
x = The total number of girls
and
y = The total number of boys. 

In this equation it says "there are three times as many boys as there are girls."

So we know we would have 

3 * x = y

So now we need to solve;

We first have x + y = 80 (80 being the total number of children, as stated in the question) 

Now we want to add x to both sides.

3 * x + x = 80 + x

Now we can do

4 * x = 80/4

x = 80/4

and then we would know that 80/4 = 20

So

x = 20

20 TOTAL GIRLS.

Now we have 

y= 3 * x = 3 * 20 - = 60

60 TOTAL BOYS.

Now we can check by doing

60+20=80

So in conclusion we know that we have a total of 20 girls and 60 boys.