Here, MNOP is a cyclic quadrilateral.
Given, ∠P=4x+12,∠N=3x+28.
We know, in a cyclic quadrilateral, the sum of opposite angles are supplementary, i.e. 180o.
Here, ∠P and ∠N are opposite angles.
Then, ∠P+∠N=180o
⟹ (4x+12)+(3x+28)=180o
⟹ 4x+3x+12+28=180o
⟹ 7x+40=180o
⟹ 7x=180o−40o
⟹ 7x=140o
⟹ x=20o.
Then, ∠P=4x+12=4(20o)+12=80o+12=92o
and ∠N=3x+28=3(20o)+28=60o+28=88o.