.774atm
First, look at what you have and look at the equations you can use to solve this problem. The best equation would be PV=nRT.
P being pressure, V being volume, n being moles, R being the gas constant, and T being temperature.
Before you start doing any of the math, make sure of two things. Since you're looking for pressure, you'll need a gas constant. When I did the problem, I used the gas constant of atm or atmospheres which is .0821.
Also! Remember to always convert celsius into kelvin, to do this, add 273 to the given celsius degree. After this is all set and done, your equation should look like this:
P =
The reason that the equation is divided by the volume is due to the fact that you need to isolate the variable or pressure.
Multiply everything on the top and divide by the bottom and you should receive the final answer of .774atm.
Hope this helps!