Question 562230
Hi, let's denote the effect of the marble machine by the function,

f(n)=2n+24

Where we input n marbles and output 2n+24 marbles.

One day x marbles were input and thus f(x) marbles were output.  Then f(x) was input and thus output was f(f(x)) marbles, but as written in the problem was 360 marbles.

So we solve f(f(x))=360 for x

Therefore, we have

f(f(x))=f(2x+24)=2(2x+24)+24=4x+72=360

So, x=72, which was the original number of marbles input.