Final answer:
There are 21 mathematics majors and 325 computer science majors in a college. The number of ways to pick a representative who is either a mathematics major or a computer science major is 346.
Step-by-step explanation:
To find the number of ways to pick a representative who is either a mathematics major or a computer science major, we can simply add the number of mathematics majors and the number of computer science majors together. In this case, there are 21 mathematics majors and 325 computer science majors, so there are a total of 346 students who are either mathematics majors or computer science majors. Therefore, the correct answer is 346 (option a).