alleryStart learning →The sum of twice a number and seven is 15. What is the number?
An = 4
Bn = 8
Cn = 11
Dn = 22
Answer & Solution
Correct answer: A. n = 4
1. Let n represent the unknown number and translate the sentence: 2n plus 7 equals 15.
2. Subtract 7 from each side: 2n equals 8.
3. Divide each side by 2: n equals 4.
4. Checking, twice 4 is 8, and 8 plus 7 equals 15, so the number is 4.
5. Dividing 15 by 2 first without subtracting the 7 would give the wrong starting point for isolating n.
_Source: OpenStax Prealgebra (CC BY 4.0), Ch 9 "Math Models and Geometry", section 9.1 Use a Problem Solving Strategy_
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