The equation that you have written in your question is incorrect because it is not balanced and it is unable to be balanced as written. For example, the number of carbon atoms in the starting reagent is 2 while there is only a single carbon atom in the products. I suspect the equation that you meant to write is shown below:
CaC2O4*2H2O --> CaO + CO2 + CO + 2H2O
As written above, this a complete, balanced chemical equation. We are asked to find the number of grams of CaO produced when 50 g of CaC2O4*2H2O is decomposed. We need to convert the 50 g into moles:
50 g * (mole/164.1 g) = 0.305 mole CaC2O4*2H2O
We see from the balanced equation that one mole of starting reagent produces one mole of CaO. So we know that the total moles of CaO produced will be 0.305. Now we need to convert this to grams:
0.305 moles CaO * (56.1 g/mole) = 17.1 g CaO
So 17.1 grams of CaO will be produced.