<PRE><B>Question 18209</B>
A and B are the whole numbers

A + B = 123

A - B = 45
-A    = -A         subtract a from both sides
-B = 45 -A         
 B = A -45         multiply both sides by  -1
A + (A-45) = 123   substitution
2A -45 = 123       add 45 to both sides
2A = 168           divided both sides by 2
A = 84
84 - B = 45        substitution
-B = -39           subtract 84 from both sides
B = 39             multiply both sides by  -1

A= 84, B=39
84 + 39 = 123      check answers
84 - 39 = 45 
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