Question 1043198
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x + y = q,   (1)  (where x is the bigger number, y is the smaller)
x - y = 3.   (2)

Add these two equations (both sides). You will get

2x = q + 3.

Hence, x = {{{(q+3)/2}}}.

For y, distract (2) from (1). You will get

2y = q-3.

Hence, y = {{{(q-3)/2}}}.

It is what you asked for.
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