Question 855741
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Let the 10's digit be x
Then unit's digit is 2*x + 1
Number itself is {{{10*x + 2*x + 1 = 12*x + 1}}}
Adding 36 to the number gives: {{{12*x + 1 + 36 = 12*x + 37}}} -- (1)
This is equal to the number with digits reversed i.e. one's digit is x and
10's digit is 2*x + 1
Value of the reversed number is {{{10*(2*x + 1) + x = 20*x + 10 + x = 21*x + 10}}} --(2)
Equating (1) and (2), since they both refer to the same number:

{{{12*x + 37 = 21*x + 10}}}
Simplifying:
{{{9*x = 27}}} or {{{x = 3}}}

So 10's digit is 3 and one's digit is 3*2 + 1 = 7.
The number is {{{highlight(37)}}}
Adding 36 gives 73 which is the reversed number - correct!

Hope you got it :)
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