Question 343943
 which is the 2-digit number that is 3 times its 
first digit plus 5 times its second digit?
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Let the number be 10t+u.
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Equation: 
10t+u = 3t+5u
7t = 4u
t = (4/7)(u)
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Since both t and u are singel digits,
u must be 7.
Then t must be 4
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The number is 47
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Check: 47 = 3*4+5*7 = 12 + 35 = 47
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cheers,
Stan H.