Question 1082714
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The sum of the {{{highlight(cross(digit))}}} digits of the two {{{highlight(digit)}}} {{{highlight(cross(numbers))}}} number is 5.
If 10 times the tens digit is added to 4 times the unit digit,
the number obtained is in the reverse order of the {{{highlight(cross(digit))}}} digits of the original number. find the number?
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<pre>
The equations are 

t + u = 5,          (1)    (where t is the "tens" digit, u is the "units" digit.)
10t+4u = 10u + t.   (2)

Simplify:

t + u = 5,
9t = 6u.

t = 5-u,
9*(5-u) = 6u,

45 - 9u = 6u,

45 = 15u  --->  u = 3,  t = 2.

The original number is 23.
</pre>