To give every angle a label:
First angle = 2x
Second angle = x
Third angle = x + 68
So, because the sum of the interior angles of the triangle is 180°, we can say that: 2x + x + (x + 68) = 180
2x + x + x = 4x
4x + 68 = 180
Isolating for x we get: x = (180-68)/4 x = 28
Because the first angle is twice as large and the third angle is greater than the second angle, the measure of the smallest angle is 28°.