Interior angle of a polygon -
144n = 180 n - 360
144n - 180n = 180n - 180n - 360
n = 10
n = 10, that means that the polygon is a 10-sided polygon or DECAGON.
The remaining problem is its number of diagonals.
Number of diagonals =
The regular polygon that has an interior angle of 144 degrees has 35 diagonals.