Question

the sum of a two digit number and the number obtained by interchanging its digits is 99 .find the number​

Answer 1

let the no. be 10x+y
=the sum of the two no. 10x+y=99. =sum after interchanging digit is .10y+x=99
by elimination method
10(10x+y=99)
x+10y=99
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99x=990-99

99x=891

x=9
now put x =9 in one of the eqn
then you get y=9