There are only certain numbers that can result from the specified formula -- 9, 18, 27, etc.; the multiples of 9 in fact. Try it -- whatever number you choose, the formula gives a multiple of 9.

Now notice that every multiple of 9 in the chart has the same symbol. Coincidence? I don't think so wink

Regards.

Finegrain
Woodinville
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Regards.

Finegrain
Woodinville