Question 4:
 2x + 3y = 17 -- equation 1
 5x + 6y = 32 -- equation 2
 (equation 1) * 2
 4x + 6y = 34 -- equation 3
 (equation 2) - (equation 3)
 x = -2 -- equation 4
 plug (equation 4)'s value of x into (equation 1)
 2(-2) + 3y = 17
 3y - 4 = 17
 3y = 21
 y = 7
 Thus the answer is x = -2 and y = 7
Question 5:
 The vertex form of a quadrilateral looks like this:
 

- a : coefficient of 
  
- (h,k): coordinate of the vertex.
 The x-coordinate of the vertex is equal to '-b/2a'. Where b is the 
 coefficient of x, so:
 

 
 There is also another formula to find the y-value of the vertex 
 coordinate, but the easier way to find it is to plug it into the original 
 equation:
 

 Since we know now that h = 4 and k = -4 and that a = 1, lets plug it into 
 the original equation.
 

 Thus the answer is 

Hope that helps!