Question

Mr. Alfred's favorite number plus Mr. Coble's favorite number is 28. The difference between Mr. Alfred's number and twice Mr. Coble's number is 10. What is Mr. Coble's favorite number? *

Answer 1

Mr. Alfred's favorite number (A)

Mr. Coble's favorite number (C)

A + C = 28 (I)

A - 2C = 10 (II)

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Solving the equations system by substitution

Rearranging (I)

A + C = 28

A = 28 - C

Replacing (I) in (II)

(28 - C) - 2C = 10

28 -3C = 10

3C= 28 - 10

C= 18 /3

C= 6

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Answer

Mr. Coble's favorite number is 6

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Verifying

A = 28 - C

A= 22 (Mr. Alfred's favorite number )

A + C = 28 (I)

22 + 6 = 28

A - 2C = 10 (II)

22 - 6*2 = 10

22- 12= 10

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