Final answer:
For the system of equations to have infinitely many solutions, the equations must represent the same line. Upon transforming the second equation, it becomes apparent that 'a' must be 2, and 'b' must be 8, leading to the calculation that a/b is 1/4.
Step-by-step explanation:
The student is working with a system of linear equations with constants a and b. For the system to have infinitely many solutions, both equations must represent the same line. This means that the coefficients of the corresponding variables must be proportional.
The second equation can be transformed by dividing every term by 2, resulting in x + 4y = 30. Comparing this to the first equation ax + by = 12, we can see that for them to be the same line, the coefficients of x and y in both equations must be proportional, and the constants must also align.
Thus, a/1 = b/4 = 12/30. Simplifying the fraction on the right side gives us 2/5. Therefore, equating a/1 to 2/5, we find that a must equal 2. Equating b/4 to 2/5, we find that b must equal 8. As a result, the value of a/b equals 2/8, which simplifies to 1/4.