For every 3 girls, there are 4 boys. if there are nine girls, that expands to three extra boys, because for every three theres an extra one. so there are 12 boys (9+3.) the final ratio, boys to girls, is 12:9.
D has the commutative property because it just flip flopped the numbers.
you said you will give use 20 points but it is marked as 5 Points.
12x > 18x - 27 - 15
12x > 18x - 42
12x - 18x > -42
-6x > -42
x < -42/-6
two negatives make a positive so now its x < 42/6
Lastly divide 42/6 so it can equal 7
Answer: X < 7.