A college student completed some courses worth 3 credits and some courses worth 4 credits. The student earned a total of 5% credits after
completing 18 courses. How many courses worth 3 credits did the student
complete?
A. 13
B. 5
C. 20
D. 39

Step-by-step explanation:

Note: It seems typo in the question. 5% should read 59.

Let 3 credit courses = x, 4 credit courses = y

As per  given we have following equations:

Solve the system by elimination. Multiply the first equation by 4 and subtract the second one:

The answer is 13

Correct choice is A

1. d.90

2. e. none of these (80)

3. a. 0

4. b. 6

5. e. none of these (10)

6. a. 5

80x^8−68x^6+16^5−20x^4−4x^3+8x^2

hope i'm right lol