How do this pls help

[orchid meteor]

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[tight lava]

Well, one way to better understand any exercise, is writing down one iteration at a time, possibly with some input.

So, let's give it a try with some simple numbers. Let's say:
a=3
b=3

b is equals to 1?
No, so I go into the else branch.

return a + mystery(a, b-1)
so,
return 3 + mystery(3, 2)
So, we have to mentally PAUSE things here, and solve the same function once again with these new inputs
Let's call this Pause-point-1 and go on, calling that function again.

At this stage:
a = 3
b = 2

b is equals to 1?
No, so I go into the else branch.
return a + mystery(a, b-1)
so
return 3 + mystery(3, 1)

So, we have to mentally PAUSE things here again, and solve the same function once again with these new inputs
Let's call this Pause-point-2 and go on, calling that function again.

At this stage:
a = 3
b = 1

b is equals to 1?
YES! Finally!
I return a
so, return 3

Now, we can UNPAUSE the least thing we paused.
What was that?
it was at Pause-point-2:

we had paused the code:
return 3 + mystery(3, 1)
but now we know that mystery(3,1) gave a result of 3
so, this became: return 3 + 3
basically return 6

We can now go on, and UNPAUSE the remaining thing we paused.
It wat at Pause-point-1 on the code:
return 3 + mystery(3, 2)

now, we know that mystery(3,2) gives us 6, so it became:

return 3 + 6
basically return 9

We have nothing else paused, so the algorithm finally ends, and the result is 9.

[tight crane]

thank you sir

[orchid meteor]

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