I'm assuming that you're working with gas laws here. This would be relating to Charles's Law which states that the volume of a gas is proportional to the temperature when pressure is held constant (or that when temperature increases, the volume increases). The formula looks like this:
[tex] \frac{V1}{T1}= \frac{V2}{T2} [/tex].
You're given T1=278 K and T2=231 K. You need a V1 (which usually is given to you). Plug the numbers into the formula and solve for V2. Good luck!