We know that,
For any polygon, sum of interal angles
=(n−2)×1800
[Where n= total number of sides]
Now,
Triangle has 3 sides. So, sum of all internal angles
=(n−2)×1800
=(3−2)×1800
=1800
Pentagon has 5 sides. So, sum of all internal angles
=(n−2)×1800
=(5−2)×1800
=5400
Hexagon has 6 sides. So, sum of all internal angles
=(n−2)×1800
=(6−2)×1800
=7200
Quadrilateral has 4 sides. So, sum of all internal angles
=(n−2)×1800
=(4−2)×1800
=3600