Using the M1V1=M2V2 equation, and converting molarity into moles per liter, this turns into:
(0.9730 moles/1L)(5 mL) = (M2)(20 mL + 5 ml) then converting mL to L using 1 L= 1000 mL:
(0.9730 mol/L)(0.005 L)=(M2)(0.020 L + 0.005 L) then algebraic simplification and shuffling:
(0.9730 moles)(0.005 L) = (M2)
(0.025 L)
the important thing to remember is that you are starting out with 5 mL and adding 20 additional, therefore you will have 25 mL diluted solution as your V2 quantity.