If 10,000 kilocalories (kcal) of energy were contained in the primary producers (trophic level 1), on average how many kcal of energy would you expect to be transferred to second-order consumers (trophic level 3)?

Explanation:

Energy transfers from autotrophs ( producers) to heterotrophs (consumers).

In this way approx 90% of the total energy is consumed by each trophic level, means only 10% energy is transferred  from each tropic level.

So as given here, in primary trophic level ( producers), total energy is 10,000 kcal.

Now the 90% (9000 kcal) of this energy is consumed( like in the form of heat and respiration) in trophic level 1 and 10% (1000kcal )is transferred to the trophic level 2( first-order consumers).

And from this energy 90%(900kcal) is consumed in trophic level 2( first-order consumers) , so only 10% (100 kcal) is transferred to the trophic level 3 (second-order consumers).