Question 365359
let tens digit be x
units digit be y
..
y=2x+1
y-2x = 1.............1
x+y = 10.............2
..
multiply equation 2 by 2
2x+2y=20
add this to equation 1
2x-2x+2y+y=21
3y=21
y = 7
x= 3
number = 37
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