first you need to have a reaction----> NaOH +HCl -> H2O + NaCl
since it is one-to-one ration between NaOH and HCl(because of the coefficients), this simplifies the calculations and you can use a dilution formula C1V1= C2V2, where C1= 0.500 M, V1= ?, C2= 0.15 M and V2= 60.0 mL.
so, (0.500 M) (V1)= (0.15 M) (60.0 mL)= 18.0 mL
