If 392cm2 of helium at 32c and 925 torr are cooled to -15c and the pressure is reduced to 775 torr, calculate the new volume the gas will occupy

The answer is 553 cm³.
Solution:
Assuming ideal behavior of the helium gas, we can use the universal gas law equation
     P1V1/T1 = P2V2/T2
The terms with subscripts of one represent the given initial values while for terms with subscripts of two represent the final conditions. 
We rearrange the gas law equation to calculate for the new volume V2:
     V2 = P1V1T2 / P2T1
We can now substitute the values to the expression. Therefore,
     V2 = (925torr * 392cm3 * 258.15K) / (305.15K * 775torr)
     V2 = 396 cm³ or 396 553 mL

Adozen is 1221/12 = 1.751.75 x 12 = 21therefore, 1.75 is the answer.

Less stable  hope this