Because the sum of the angles in a triangle is 180 degrees, and one angle is diagonal, the sum of the other two angles is equal.
The second question, four
The third question can be concluded from the first question:
Angle C+ angle CAP= angle P+ angle PDC. . . 1
Angle C+ angle CAB= angle B+ angle CDB. . . 2
Because the angle is divided into two, there are:
2-corner cap = corner cab, 2-corner PDC= corner CDB.
1*2-2:
Angle C = 2° Angle P- Angle b
Angle P=(76+80)/2=78 degrees.
The fourth question,
Is 1*3-2:
Angle p = (2 angle C+ angle B)/3