Answer:

let unit digit is x

then ten's digit is (x+2)

according to question ,

x+x+2=1/7{10(x+2)+x}

=> 2x+2=1/7(10x+20+x)

=> 7(2x+2)=11x+20

=> 14x+14=11x+20

=> 14x-11x=20-14

=> 3x=6

=> x=6/3=2

so unit digit is 2 and ten's digit is 2+2=4

so the number is 10×4+2=40+2=42