The answer is d.42 because since the denominator(8) is being multiply by 6 to get 48, you should multiply 7 by 6 too to get the answer 42. And so the answer is 42/48.
Let's consider the equation;
7x+2=y <-- no denominator present
If you look at the graph, you will also notice that there are no possible values of x that cannot be represented through this graph. There will always be a corresponding y coordinate.
This can be applied to a wide range of equations where no denominator with an x value will have a vertical asymptote. Try to visualize a simpler situation with the same qualities if you don't know how to find the solution.
Hope I helped :)
Cube: Area cubed
Rectangular Prism: A=(wl+hl+hw)