Determine the total mass of washing soda produced if 3360. kilograms of NaHCO3 reacts completely to produce 360. kilograms of H2O and 880....

First you need the balanced chemical
equation:

2 NaHCO3 --> HOH   +   CO2   + 
Na2CO3

So if you heat two moles of baking soda, you produce
one mole of water, one mole of carbon dioxide and 1 mole of washing
soda.

In your example you have 360 kg HOH = 20 kmol;  880
kg CO2 = 20 kmol

You start with 3360 kg of NaHCO3 = 40
kmol

So you will produce 20 kmol of washing
soda.

20 kmol * 106 kg/kmol = 2120 kg of washing
soda.