Question 853708
"IF THE DIGITS ARE REVERSED"....  This means, {{{10*U+1*X}}}.


Forty five more than the original number:  {{{10U+X=45+(10X+U)}}}.



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Also, stay with one case level or the other.  Do not mix them for the same expression or the same number.  {{{M<>m}}}; {{{D<>d}}},...
... otherwise, your first two steps seem good so far.  I think your second step was going off-track.


{{{U=3X-1}}} and {{{10U+X=45+10X+U}}};
{{{10U-U+X-10X=45}}}
{{{9U-9X=45}}}
{{{9(U-X)=5*9}}}
{{{U-X=5}}}
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Substitute using the U equation ...
{{{(3X-1)-X=5}}}
{{{3X-X-1=5}}}
{{{2X-1=5}}}
{{{2X=6}}}
{{{X=3}}}----------result
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{{{U=3*3-1}}}
{{{U=9-1}}}
{{{U=8}}}----------result
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ORIGINAL NUMBER = 83.