Question 10
You can use ICE table to solve this problem
2 NH3 -----> N2 + 3H2
I 76 cm 0 0
C -2x x 3x
after decomposition a change of 6cm of Hg was observed
so sum of all changes should be equal to 6 cm of Hg
means -2x + x + 3x = 6cm
get the value of x and then partial pressure of H2 which is 3x .