How do you use mental math to find the sum or product and then identify the property or properties that you use to simplify $(27 + 8) + 12$ $(27 + 8) + 12$ ?

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Answer 1 · 2015-04-10T15:12:36

Mentally regroup
noting that $8 + 12 = 20$ $8+12 = 20$
then
$20 + 27$ $20+27$
equals a simple $47$ $47$

"Regrouping" uses the associative property.

How do you use mental math to find the sum or product and then identify the property or properties that you use to simplify (27+8)+12(27 + 8) + 12?