At s.t.p, the volume of a gas =22.4dm³
Talking the problem,
At 1atm, 273K the volume =7 moles *22.4dm³/mol
At 323K, 2.90atm, volume =?
The combined gas equation
P1v1/T1=P2v2/T2
P1=1atm
P2=2.9atm
T1=273K
T2=323K
V1=156.8dm³
Therefore,
1*156.8dm³/273=2.9atm*V2/323
V2=(156.8dm³*323K)/(273K*2.9atm)
= 64dm³