Answer:
45 girls
Step-by-step explanation:
If 60% of the class is girls then 40% of the class is boys.
30 boys are in the class, meaning that 40% of the class comprises those 30 boys
First, we need the total number of class members: 30/x = 40/100 -> 40x=3000 -> x=3000/40 -> x=75
Now that we know the total class members, at 75, we can calculate the number of girls in the class. You can do this:
0.6*75=45
or
60/100=x/75 and solve for x