Show that the set of all positive length string {a, b} is countale

In a class, there are 12 girls. if the ratio of boys to girls is 5: 4 how many boys are there in the class

If your teacher tells you to do questions 6 through 19 in your math book for homework, how many questions is that

3women sell hats at a craft fair weekly. the money they make at the fair is split into categories. 9% goes to pay taxes. $55 goes to pay rent for the space they sell in. the rest is split between the women. if the group make $706 at the fair, how much does each women get paid once the money is divided