One thing when solving these problems, you always want to start with what you are give:
Mass of flask=25.62 g
Mass of flask + H2O=256.9 g
Density of H2O=0.987 g/cm^3
The first question asks what is the volume of the water (mL) in the flask.
The first thing that you have to figure out is how much of the mass of the flask is the actual flask and how much is water. You can solve this by subtracting the mass of the flask from the mass of the flask + water.
256.9g - 25.62g = 231.28g
You should now be able to use this number to solve for volume using the Density formula. D=m/V
V=m/D (look in your givens to find this number)
Once you find the volume, you can use that number to answer the next part of this problem;
Once again you can use D=m/V formula to now solve for mass.
You should use the volume you found in the first part of the problem
Once you find the mass you can add it to the original given mass of the flask and this will answer your second part. Make sure you pay attention to units and to sig figs.