Calculate the amount of water which should be added to 80% solution of Sulphuric acid to make it a 50% solution?

Concentration of Sulphuric acid = 80%
So in a 100cc, Sulphuric acid = 80cc and water = 20cc
Let x be the amount of water added to make concentration of 50%
⇒80/(100+x) = 50/100
⇒ 80/(100+x) = 1/2
∴ x = 60cc