SOLUTION: If the difference between one-third of a number and one-seventh of that same number is 8, then what is the number? (A) 12 (B) 21 (C) 30 (D) 42 (E) 56

Algebra ->  Customizable Word Problem Solvers  -> Numbers -> SOLUTION: If the difference between one-third of a number and one-seventh of that same number is 8, then what is the number? (A) 12 (B) 21 (C) 30 (D) 42 (E) 56       Log On

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Question 324914: If the difference between one-third of a number and one-seventh of that same number is 8, then what is the number?
(A) 12 (B) 21 (C) 30 (D) 42 (E) 56

Answer by vleith(2983) About Me  (Show Source):
You can put this solution on YOUR website!
Let x be the number. You are told
x%2F3+-+x%2F7+=+8 find a common denominator. Since 3 and 7 are relatively prime (and also really prime), that demoninator is 3*7 = 21
7x%2F21+-+3x%2F21+=+8
4x%2F21+=+8
4x+=+168
x+=+42
Check your answer
what is the difference between 42/3 = 14 and 42/7 = 6 equal 8??