Let the numbers be x, y and z,
Where y is the smallest number, so,
By question,
1st case,
x=2y ........eq(1)
2nd case,
z=y+11 ........eq(2)
Finally, 3rd case,
x+y+z=79 .....eq(3)
Equating the values of x and z from eq(1) and eq(2) in eq(3), we get,
(2y)+y+(y+11)=79
Or, 2y+y+y+11=79
Or, 4y=79-11
Or, 4y=68
Or, y=68/4
.•. y=17,,
Hence, the smallest number is 17.