Answer: 0.66
Explanation:
He must choose 2 courses.
The options are:
one of two science classes
one of three social sciences classes.
For the first class selection we do not have any restriction, so that selection can be ignored.
Now, we can assume that one of the 3 social sciences is economics, so we have 2 classes that are not economics.
Then, the probability that he does not select economics (if the selections are at random) is equal to the number of classes that are not economics divided the total number of classes:
p = 2/3 = 0.66