Concept of partial pressure is to be applied here.
Let the partial pressure of ArAr in the final mixture be p_"Ar"pAr
Initially before mixing ArAr had
Pressure P_"Ar"=1.29PAr=1.29 atm
TemperatureT_"Ar"=223+273=500TAr=223+273=500 K
Volume V_"Ar"=0.600VAr=0.600 L
In the mixture it acquires
Pressure p_"Ar"=?pAr=? atm
Temperature T_"mAr"=23+227=250TmAr=23+227=250 K
Volume V_"mAr"=0.400VmAr=0.400 L
So by combined Boyle's and Charles's equation for ideal gas we can write
(p_"Ar"xxV_ "mAr")/T_"mAr"=(P_"Ar"xxV_"Ar")/T_"Ar"pAr×VmArTmAr=PAr×VArTAr
=>p_"Ar"=(P_"Ar"xxV_"Ar")/T_"Ar"xxT_ "mAr"/V_"mAr"⇒pAr=PAr×VArTAr×TmArVmAr
=>p_"Ar"=(1.29xx0.600)/500xx250/0.400=0.9675⇒pAr=1.29×0.600500×2500.400=0.9675 atm
Again let the partial pressure of O_2O2 in the final mixture be p_(O_2)pO2
Initially before mixing O_2O2 had
Pressure P_(O_2)=535PO2=535 torr ~~0.535≈0.535 atm
TemperatureT_(O_2)=106+273=379TO2=106+273=379 K
Volume V_(O_2)=0.200VO2=0.200 L
In the mixture it acquires
Pressure p_(O_2)=?pO2=? atm
Temperature T_(mO_2)=23+227=250TmO2=23+227=250 K
Volume V_(mO_2)=0.400VmO2=0.400 L
So by combined Boyle's and Charles's equation for ideal gas we can write
(p_(O_2)xxV_ (mO_2))/T_(mO_2)=(P_(O_2)xxV_(O_2))/T_(O_2)pO2×VmO2TmO2=PO2×VO2TO2
=>p_(O_2)=(P_(O_2)xxV_(O_2))/T_(O_2)xxT_ (mO_2)/V_(mO_2)⇒pO2=PO2×VO2TO2×TmO2VmO2
=>p_(O_2)=(0.535xx0.200)/379xx250/0.400=0.1765⇒pO2=0.535×0.200379×2500.400=0.1765 atm
So total pressure in the flask
P=p_"Ar"+p_(O_2)=0.9675+0.1765=1.144P=pAr+pO2=0.9675+0.1765=1.144 atm