Question 319076
Let AB be your digit or numerically 10*A+B. 
The reverse digit number is BA or numerically 10*B+A.
1.{{{A=2B}}}
.
.
{{{10A+B+10B+A=66}}}
{{{11A+11B=66}}}
2.{{{A+B=6}}}
Substitute eq. 1 into eq. 2,
{{{2B+B=6}}}
{{{3B=6}}}
{{{highlight(B=2)}}}
Then from eq. 1,
{{{highlight(A=4)}}}
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.
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The original number is 24, the reverse number is 42.