Write the rule to describe the transformation

First, we have rounded numbers A and B, and we know that:

A + B = 11000

A - B = 3000

Now we can solve this system of equations by isolating one variable in one of the equations, i will choose A in the second equation:

A = 3000 + B.

Now we can replace this into the other equation:

3000 + B + B = 11000

2*B = 11000 - 3000 = 8000

B = 8000/2 = 4000

and:

A - 4000 = 3000

A = 3000 + 4000 = 7000.

But remember that our original numbers are not exactly whole numbers, they are rounded up, so we could write them as:

A = 6999.8 (that would be rounded up to 7000)

B = 3999.7 (that would be rounded up to 4000)

The sum is:

A + B = 10999.5 (notice that this would be rounded up to 11000)

A - B =  3000.1 (this would be rounded down to 3000)

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