SOLUTION: twenty-one is three times the difference between four times a number and five. find the number.

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Question 866: twenty-one is three times the difference between four times a number and five. find the number.
Answer by usyim88hk(158) About Me  (Show Source):
You can put this solution on YOUR website!
First, make an equation!!!
Let the number be x:
21=%28%284%2Ax%29-5%29%2A3 or 21=%285-%284%2Ax%29%29%2A3 (Let's slove the first one first)
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First equation:
21%2F3=%284x-5%29%2A3%2F3
7 = 4x-5
7+5 = 4x-5+5
12 = 4x
[x = 3]
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Second equation:
21%2F3+=+%285-4x%29%2A3%2F3
7 = 5-4x
7+4x = 5
4x = -2
[x = -1/2 or -0.5]
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[x = 3 or -0.5] (ANSWER!!!!)