Question

V1=3m3,P1=1.2KPa T=const

How much will be change P if

A) volume reduced to 1.5 ,2 and 2.5
B) volume increase to 1.5 ,2 and 2.5

Answer 1

Is this Boyle's law?

P1V1=P2V2

or P2V2=P1V1=constant

So figure out the constant (P1V1)

then P2=constant/V2=3.6/1.5

Now that is the actual pressure. Your question asks what will be change P. I don't know what that means. Change is normally P2-P1, but for the life of me I don't know why a competent teacher would find that. Now you teacher might have had in mind the ratio, P2/P1, but I just don't know.
The best I can do is help you find the new pressure, as above.