There are two distinct ways a test taker could complete a total of 8 questions, while completing at least 2 from each section:
• complete 4 from one section, and 2 from the other two sections
• complete 2 from one section, and 3 from the other two sections
If the test taker will complete 4 questions from one section, she has 5 choices (5C4 if you like) for which questions to do. She then has 5C2 = (5)(4)/2! = 10 choices for each of the other two sections. Since there are three choices for which section to do the four questions from, there are (3)(5)(10)(10) = 1500 ways to complete four questions from one section, and two from the other sections.
Similarly, if the test taker will do 2 questions from one section, she has 5C2 = 10 choices for those questions. For the two sections where she completes 3 questions, she has 5C3 = (5)(4)(3)/3! = 10 choices. Since she has three choices for the section from which to complete the two questions, there are (3)(10)(10)(10) = 3000 ways to complete two questions from one section, and three from the other sections.
Adding the results from each case, the answer is 1500+3000 = 4500.