Question

a number has two digit whose sum is 7.if 9 is added to the number ,it's number get interchanged.find the number

Answer 1

let no be XY

X + Y =7

X×10 + Y +9 = Y×10 + X

X0 + 7 - X+9 = (7-x)10 +x

9x + 16= 70 - 10x +x

18x= 54
x=3

y=4


SO NO IS 34