Answer:
So the number of total combinations is 35.
Step-by-step explanation:
We know that Ellen must take 4 courses this semester. She has a list of 3 math courses and 4 science courses.
Therefore, she have total 7 courses.
So, we calculate the number of combinations to choose 4 out of 7 courses.
We get:
[tex]C_4^7=\frac{7!}{4!(7-4)!}=35\\[/tex]
So the number of total combinations is 35.