Boltzmann's constant/Maxwell-Boltzmann dist. of molecular speed help

MasterMatrix8

1. The problem statement, all variables and given/known data
Calculate the V_rms for U²³⁵F₆ at 375 degrees C. What % of the molecules have V_rms>500 m/s?

I'm not entirely sure on what direction to go in, sadly I missed the day he covered making these graphs and doing these types of problems. I do have all the formulas though.....but again I'm not sure on how to use them. Any help would be much appreciated, Thank you.

P.s.- I talked to the teacher and he said it would have kg and joules as it's units, that's why I put the MM of U²³⁵F₆ in kg, hopefully I'm right. Haha. Thanks again.


2. The attempt at a solution

3(.08206)(648) <------all this is under a square root
.348988