How much water would you add to 175ml of 6.00 m hydrochloric acid to prepare a 2.00 m solution of this acid?

We can use the dilution formula to find the volume of the diluted solution to be prepared first
c1v1 = c2v2 
where c1 - concentration and v1 - volume of the concentrated solution 
c2 - concentration and v2 - volume of the diluted solution 
substituting the values
6.00 M x 175 mL = 2.00 M x V
V = 525 mL
volume of diluted solution is 525 mL
then volume of 6.00 M HCl acid taken is 175 mL
therefore volume of water to be added is - 525 - 175 = 350 mL
350 mL of water should be added