There are three groups. One group for girls. One group for half the boys which is equal to one group of girls and another identical sized group of boys because there are twice as many boys as girls.
48=total 3=number of groups
48/3=16
16 is equal to the number of girls because it is equal to half the number of boys
16*2=32
32+16=48
Number of boys plus number number of girls: 32+16=48
If she works 40 hours or less then she earns 20x dollars. If she works more than 40 hours, then she earns 20×40 dollars for the first 40 hours and 30×(x-40) dollars for <span>every hour over 40 hours. The number of hours over 40 hours is x-40.</span>