In a math class with 25 students, a test was given the same day that an assignment was due. There were 15 students who passed the test and 20 students who completed the assignment. There were 13 students who passed the test and also completed the assignment. What is the probability that a student passed the test given that they did not complete the homework?

Ithink the answer is a.3: 1i hope this

So the first thing we do is to multiply the top equation by 3. the reason i want to do this is i notice there will be a 6y on both equations and can possibly add/subtract them. so we get 6y = -3x + 27. adding that and the second equation we get 6x = 27-15 which is 12. divide by 6 and we get 2. ∴ x = 2. substituting 2 into the first equation we get 2y = -2 + 9 which is 7. divide by 2 and we get 7/2. ∴ y = 7/2, x = 2.