Question 1009649
.
x and y are the numbers
.
x-y=3
x=y+3 . Use this to substitute for x below.
.
x+y=5 . Substitute for x from above
(y+3)+y=5
2y=2
y=1
.
x=y+3
x=1+3
x=4
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OR:
________________________________
x+y=5
x-y=3 . Add the two equations
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2x=8
x=4
.
x+y=5
4+y=5
y=1
. 
CHECK:
x-y=3
4-1=3
3=3