Agas is contained in a thick walled balloon. when the pressure change from __ torr to 777 torr, the volume changes from 2.58 l to 1.53 l and the temperature changes from 368 k to 495 k

Answer is 342.6 torr.

Explanation:
Let's assume that the gas in the balloon is an ideal gas. 

Then we can use combined gas law, 
PV/T = k (constant) 

Where, P is the pressure of the gas, V is volume of the gas and T is the temperature of the gas in Kelvin. 

For two situations, we can use that as,
P₁V₁/T₁= P₂V₂/T₂ 

P₁ = ?
V₁ =  2.58 L
T₁ = 368 K
P₂ = 777 torr
V₂ = 1.53 L
T₂ = 495 K 

From substitution,   
     P₁ x 2.58 L / 368 K = 777 torr x 1.53 L / 495 K                             
                               P₁ = 342.6 torr

Hence, the answer is 342.6 torr.

Ibelieve it is b. proton.hope my answer has you : )