In a group of 29 children, there are twice as many boys than girls. how may girls are there?

B + g = 29

b is boys
g is girls

also, another equation is

2g = b

Plug that equation into the first one, and we get:

2g + g = 29

3g = 29

g = 29/3 = 9.667

But there can't be 0.667 of a girl, so we have to round down to 9.

Your answer is 9 girls.

There are (9 and 2/3) girls and (19 and 1/3) boys.