A student can take three subjects in 40 ways.
SOLUTION:
Given that, there are 4 different math courses, 5 different science courses, and 2 different history courses.
A student must take one of each, how many different ways can this be done?
Now, number ways to take math course = 4
Number of ways to take science course = 5
Number of ways to take history course = 2
So, now, total possible ways = product of possible ways for each course = 4 x 5 x 2 = 40 ways.
Hence, a student can take three subjects in 40 ways.