Subtract the mass of the filter paper (0.27 g) from the mass of the paper and copper (0.98 g).

0.71 g

Explanation:

In laboratory experiments, we typically measure the initial mass of the filter paper and then measure the mass of the filter paper and the recovered compound altogether. This is done in order to find the exact mass of the precipitate recovered and not to lose any of it while scraping it off.

The difference between the mass of the paper and copper and the mass of the filter paper would be:

the temperature of the gas, in k, not celsius.