we can use the formula:
C1V1 = C2V2
Where,
C1 = initial concentration,
V1 = initial volume,
C2 =final concentration,
V2 = final volume.
Now,
C1 = 0.749 M
V1 = 17.7 mL
V2 = 17.7 mL + 55.3 mL = 73 mL
C2 = ?
from formula,
C2 = (C1V1) / V2
put the value in formula,
C2 = (0.749 M x 17.7 mL) / 73 mL
C2 = 0.181 M
Therefore, the concentration of the diluted solution is 0.181 M.