alleryStart learning →The sum of two numbers is 39. Their difference is 9. Find the numbers.
A39 and 9
B15 and 24
C21 and 18
D24 and 15
Answer & Solution
Correct answer: D. 24 and 15
1. Let n and m be the two numbers, giving the system n + m = 39 and n - m = 9.
2. Add the two equations to eliminate m: 2n equals 48, so n equals 24.
3. Substitute n = 24 into n + m = 39 to get m equals 15.
4. Check: 24 plus 15 equals 39, and 24 minus 15 equals 9, so both conditions hold.
_Source: OpenStax Elementary Algebra (CC BY 4.0), Ch 5 "Systems of Linear Equations", section 5.3 Solve Systems of Equations by Elimination_
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