This question checks whether you know the everyday meaning of the phrase "as easy as pie". People use this phrase for a task that takes almost no effort to finish.
The correct option is "Very simple", because the speaker is telling us the problem turned out to need almost no effort to solve.
Let's summarize:
So the option that best expresses the meaning of "as easy as pie" is "Very simple".
If the price of a commodity increases by 25%, by what percentage should the consumption be reduced to keep the expenditure the same?