I think it’s six because 3n=6-5 3 n=6-5 then subtract 5 5 from 6 6
 
        
             
        
        
        
Answer:
Step-by-step explanation:
a) A square is a rectangle.   True
Reason: Property of Rectangle: (i) Opposite sides are equal and parallel. (ii) Each angle is 90 (iii) Diagonals are equal and bisect each other.
A square hold all these properties. A square is  a rectangle.
b) A polygon with 21 sides has 432 possible diagonals. False
Reason: Number of diagonals of a polygon = 
n --> number of sides of a polygon.
=  = 189 diagonals
 = 189 diagonals
c) All three angles in an Isosceles triangle are equal. False
Reason: In an isosceles triangle, two angles are equal.
If three angles are equal, then that is an equilateral triangle.
d) The measures of the exterior angles of a nonagon, a nine-sided figure, have a sum of 360°. True.
Reason: The sum of measures of the exterior angles  of any polygon is 360
 
        
                    
             
        
        
        
59° + 81°+ x° = 180°
140° + x° = 180°
x = 40°
        
                    
             
        
        
        
Answer:
The missing side length is 3 units long.
Step-by-step explanation:
Use the Pythagorean Theorem where c²=a²+b²,
c=2√3, c²=12
a²=√3, a²=3
Solving for the missing side yields a side length of 3.