To find the total mass of both pieces of furniture, you will add the 2 amounts together if the units are the same. In the example, they are not the same.
If the answer need to be in grams, you should covert the 7 kg to grams. (1 kg = 1000 g). 7 kg=7000 g.
So, 4048 grams + 7000 grams = 11048 grams.