The GCF is the "Greatest Common Factor". The factors of 12 are 1, 2, 3, 4, 6, 12. The Factors of 18 are 1, 2, 3, 6, 9, 18. This would mean the GCF of these two numbers are 6. The sum is obviously 30. You could do something like 3(2+8 Which would mean 3x2=6 + 3x8=24.
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