What is the final pressure of a system (atm) that has the volume increased from 0.75 l to 1.1 l with an initial pressure of 1.25 atm? 1.1 0.85 1.8 1.2 none of the above?

Boyle's law states that pressure is inversely proportional to volume of gas at constant temperature 
PV = k
where P - pressure , V - volume and k - constant 
P1V1 = P2V2
where parameters for the first instance are on the left side and parameters for the second instance are on the right side of the equation 
substituting these values in the equation 
1.25 atm x 0.75 L = P x 1.1 L
P = 0.85 atm 
final pressure is B) 0.85 atm 

13) a 14) a15) b16) i don't know sorry17) a (maybe)