Question 185142
Let the number be N and the two digits be x and y

{{{10*x + y = N}}}
{{{y = N - 10x}}}
{{{10*y + x = N - 18}}}
{{{10*(N-10x) + x = N -18}}}
{{{10N - 99x = N -18}}}
{{{(9N +18)/99 = x}}}
{{{x + y = 12}}}
{{{x + N -10x = 12}}}
{{{-9x = 12-N}}}
{{{-9*(9N+18)/99 = 12 - N}}}
{{{-9N - 18 = 132 - 11N}}}
{{{2N = 150}}}
{{{N = 75}}}

Check yor answer., is the sum of the digits 12? Is the difference between 75 and 57 equal to 18?