The sum of two numbers is 23 and their difference is 7.what are the two numbers?

2
Before copying the answer of JoecelE, the equation he used is derived from the system, and you must show from where it come from.  x + y = 23; x -y = 7.  The second equation in terms of x is -y = -x + 7 or y = x - 7.  Use x + 7 in the first equation instead of y.  Therefore, x + y = 23 becomes x + (x - 7) = 23.  Simplify 2x - 7 = 23;  then, 2x - 7 + 7 = 23 + 7;  2x = 30;  2x/2 = 30/2.  x = 15.  There is only one solution:  x = 15; y = 8.  Therefore, the solution of the system is (x,y) = (15, 8) 
I mean SHOULD  derived from the system.  So in terms of x using any of the equation, x = 15 and y = 8.  When you graph the intersecting lines, the intersection is (x,y) which is (15, 8) as the point of intersection and ONLY SOLUTION to the system, and NOT (8,15).  Try plotting (15, 8) and its different from (8,15).  

Answers

2016-01-09T15:08:04+08:00
x = first integer
x + 7 = second integer

x + x + 7 = 23
          2x = 23 - 7
    2x ÷ 2 = 16 ÷ 2
            x = 8 - first integer
      x + 7 = 8 + 7 = 15 - second integer

Check:

15 + 8 = 23
15 - 8 = 7
0
Sorry, x = second integer; and x + 7 = first integer. Sorry I haven't noticed that yesterday .-.
2016-01-09T15:33:22+08:00
15 and 8
15+8= 23
15-8 = 7
basta nalang ako nag add and subtract hanggang makuha hahahhah
0
Good day! You must show your solution because the problem is a system in  Cartesian plane.  Therefore, your solution must show which is x and which is y.  There is ONLY ONE solution, and 15 and 8 can not be interchanged, one is the abscissa, and the other is the ordinate. (x,y) cannot be (y,x)  :-)