Question 1089721
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x + y = 57.
x - y = 20.
-----------------Add the two equations. You will get

2x = 57 + 20 = 77.   Hence,  x = {{{77/2}}}  = 38.5.

Then from the first equation,  y = 57 - 37.5 = 18.5.


Two possible pairs are (38.5,18.5)  and  (18.5,38.5).
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Solved.