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1. Pick any number between 70 and 979:

2. Add it to 1979:

3. Remove the thousands digit and add it to the remaining number:

4. Now subtract your last result from your original number:

5. Your answer is 19.

Here is an example:

1. Pick any number between 70 and 979:

Pick 840.

2. Add it to 1979:

840 + 1979 = 2819

3. Remove the thousands digit and add it to the remaining number:

819 + 2 = 821

4. Now subtract your last result from your original number:

840 - 821 = 19

5. Your answer is 19.