Question

In a class of 18 there are 2 girls for every 1 boy. how many girls are there?

Answer 1

2 girls = 1 boy
12 girls = 6 boys 
12 + 6 = 18 
girls = 12

Answer 2

X-girls y-boys

if x+y=18 and 2x=y then


x+2x=18
3x=18
x=6