Give the step-by-step reasoning process and then the final answer. Two-thirds of the class have brown eyes. Half of the students with brown eyes have black hair. If there are 6 students in the class with brown eyes and black hair, how many students are there in total?
There are 6 * 2 = 12 students with brown eyes and hair of any color. There are 12 * 3 / 2 = 18 students in total.
The final answer: 18.