Question 1046935
Let {{{ t }}} = the tens digit
Let {{{ u }}} = the units digit
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{{{ 10t + u = 10u + t - 72 }}}
{{{ 72 = -9t + 9u }}}
{{{ -t + u = 8 }}}
The only thing that fits here is:
{{{ t = 1 }}}
{{{ u = 9 }}}
because if {{{ u }}} is {{{8}}} or less,
then {{{t}}} becomes zero or negative
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The number is 19 
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check:
{{{ 10t + u = 10u + t - 72 }}}
{{{ 10*1 + 9 = 10*9 + 1 - 72 }}}
{{{ 19 = 91 - 72 }}}
{{{ 19 = 19 }}}
OK