Question 1186991
u and t
ONES digit and tens digit


{{{system(u+t=13,t=u^2-17)}}}


Looking at the formula for t, the second equation and taking only from the digits,
{{{4<t<10}}}, so very few choices can be examined to see how they fit.


Try 5 for u ?
{{{t=5^2-18}}}
{{{t=8}}}
-
{{{u+t=13}}}
{{{u+8=13}}}
{{{u=5}}}
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The two digit number:    85