what is the testmaker asking me here, i.e.
how to express their question in math terms? thank you.

"On a scale that measures the intensity of a certain phenomenon, a reading of N+1 corresponds to an intensity that is 10 times the intensity corresopnding to a reading of N.
On that scale, the intensity corresponding to a reading of 8 is how many times as great as the intensity corresponding to a reading of 3?"

Think of it this way.
If a reading of N is received, we have an intensity of N.
If a reading of N+1 is received, we have an intensity of 10N
If a reading of N+2 is received, then, we have an intensity of 100N
N+3 means 1000N
The number added to N refers to the number of 0's on the power of 10.
Thus, a reading of N+8 will be 10*N^8
and a reading of N+3 will be 10*N^3
This means that n+8 is 10^5 times n+3.

(You can substitute 1 for N and see this without the variable.)

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