I can answer 18 for you, but I don't understand 16
18. Since when we lose 3 girls the ratio for the girls side drops by 1, that tells us that 1 digit equals 3 people.
a) 5*3=15 so our answer is 15 girls.
b) 4*3=12 and 5*3=15 so 15+12, our answer would be 27
