Question

what happens when the presssure is reduced in a triple point

Answer 1

Dear Student,
At triple point al the three states of matter co-exist and if we change the pressure at the triple then the equilibrium state will be disturbed and change of state will take place.
If the pressure is reduced then the corresponding temperature will increase and the following change will take place
solid$\rightleftharpoons$liquid $\rightleftharpoons$gas
Regards!