Respuesta :

you correctly said that you need the combined gas law. 

combine gas law----> P1V1/T1= P2V2/T2

P1= ?
V1= 2.58 L
T1= 368K

P2= 777 torr
V2= 1.53 L
T2= 495K

Now we plug in the values. 

(P1 X 2.58)/ 368= (777 X 1.53)/ 495 K

P1= 343 torr