Let x represent the number of girls.
Then x + 4 represents the number of boys. (there are 4 more boys than girls)
To solve this we can set up a simple equation.
# of girls + # of boys = 16 people
x + (x+4) = 16
x + x + 4 = 16
2x + 4 = 16
2x = 16 - 4
2x = 12
x = 12 / 2
x = 6
x = # of girls, so there are 6 girls.
Good luck on your math!
-Jabba