Question

The sum of two integers is 9 their difference is 5 what are the two integers

Answer 1

X+y=9     x=9-y
solve for x     
x-y=5   so substitute x by 9-y
9-y-y=5
9-2y=5 isolate 
9-2y-9=5-9
-2y=-4 divide both sides by -2
-2y/-2=-4/-2
y=2 and x=9-2=7
check for x+y=9
               7+2=9 
check for x-y=5
                7-2=5      so x=7 and y=2 

            

Answer 2

X + y = 9
x - y = 2

x = 5 + y

5 + y + y = 9
5 + 2y = 9
2y = 9 - 5
2y = 4
y = 2
----------

x = 9 - 2
x = 7
----------