<PRE><B>Question 936188</B>
Let t = tens digit
u = units digit
10t + u = value of the number
10u + t = value of the number with digits reversed 
we have two equations
t + u = 12
10u + t = 8u + 20
t + 2u = 20
subtract first equation form second equation
u = 8
t = 4
original number is 48 and the number interchanged is 84
84 = 64 +20 = 84
our answer checks
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