Could someone please help me in how to set up two Molar Mass equations?

Question

1) Given: 0.209g vapor
757mmHg
100.5 degrees celsius or 373.5 K
Volume of flask 151mL
2)2.82g gas
639mL
27degrees or 300K
1.00 atm ???
I am not sure for one thing how to find the R (ideal gas law)
M=mRT/PV

Thank you for helping me! I understand now, I wasn't sure if I had to calculate the R or if it was constant.

Answer 1

The equation is 1= mRT/PV.
You know P
You know T
You know V
You should know R =0.082 L-atm/degK-mole
(1 atm =760 mm Hg.)
So you can determine m, the moles.