SOLUTION: A 2-digit number is 12 tims its tends digit. The sum of the digits is 12. What is the tens digit?

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Question 548275: A 2-digit number is 12 tims its tends digit. The sum of the digits is 12. What is the tens digit?
Answer by josmiceli(19441) About Me  (Show Source):
You can put this solution on YOUR website!
Let the 10's digit = a
Let the unit's digit = b
given:
(1) +10a+%2B+b+=+12a+
(2) +a+%2B+b+=+12+
-------------------
(1) +b+=+12a+-+10a+
(1) +b+=+2a+
Substitute (1) into (2)
(2) +a+%2B+2a+=+12+
(2) +3a+=+12+
(2) +a+=+4+
and, since
(2) +a+%2B+b+=+12+
(2) +4+%2B+b+=+12+
(2) +b+=+8+
The 10's digit is 4