There are four boys to every five girls in an introductory geology course. If there are 387 students enrolled in the course, how many are boys?

172 boys.

Step-by-step explanation: The ratio of boys to girls is 4:5. We can say that the number of boys in the class is four multiplied by the common value that the ratio is based on. We can call this common value x and say that the number of boys in the class is 4x. Applying the same logic to the girls, we can say that there are 5x girls in the class. Thus, a total of 9x children. We divide the total value by 9 to get x, which equals 43. We can then retrieve the number of boys by calculating 4x, which equals 172.

-7/8

step-by-step explanation:

instead of subtracting you add the -6/8 and -1/8