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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 :

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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