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Stephanie851216
When you're talking about sums, that means you are adding. So, you do 8+7=15. The sum of it being doubled, you say? 15x2=30, or 15+15=30. Hope this helped :)
Huffle
Here is a hint, "sum" is adding up therefore, the question is asking "The number of 8 + 7, then multiplied by 2. 8+7x2 = 30