Question

the sum of the digits of a two digit number is 9. if the digits are reversed, the new number if 63 grater than the original number. what is the original number?

Answer 1

The number is AB
A+B=9
10B+A=63+10A+B

Those two equations will solve it.

Answer 2

7,2 ---> 2,7
5,4 ----> 4,5
1,8 ----->8,1
9,0 -----> can't be reversed because it doesn't become a two digit number.
3,6 ----->6,3
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all these two digit numbers add up to 9, and if reversed, you should subtract
72- 27= does it equal greater than 63, no
54-45= ..........................., no
81-18 = yes it does ===63

so the original number is 18