the diagonals of the rectangle have these equations. y= 4x - 10 y= -4x + 8 find where these lines intersect

hi

if it's intersect, then :  

4x-10 = -4x+8

-10-8 = -4x-4x

 -18  = -8x

 -18/-8 = x

   18/8 = x

   9*2 /4*2 = X

   9/4 = X

So X is  9/4   then y  is  :   4( 9/4) -10 =  9-10 = -1  

Lines intercept at   (  9/4 ; -1)

The value of the fifth number will be 18.

Since the average of five numbers is 12.4, their total value will be:

= 12.4 × 5 = 62

Since the average of four of these numbers is 11, their total value will be:

= 11 × 4 = 44

Therefore, the value of the last number will be:

= 62 - 44 = 18

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