Answer:

Step-by-step explanation:
Let the first angle be  = x 
Given: 
            Second angle is twice first = 2x
            Third angle is three times first = 3x 
Also given:
   Second angle is half of fourth angle, that is:
                                                                    
  Fifth angle is 20° less than fourth angle, that is: 
                                                                    
Sum of interior angles of a polygon with n sides = ( n - 2 ) x 180°
Here n = 5 ,
    therefore sum of interior angles = ( 5 - 2 ) x 180 = 3 x 180 = 540°.
That is , 
              x + 2x + 3x + 4x + ( 4x - 20 )  = 540
                                            14x - 20 = 540
                                                   14x = 540 + 20 
                                                   14x = 560
                                                      x = 40
