If the two angles form a linear pair, the sum of the angles is 180 degrees.
If the small angle is one-third of the other, then the total is 1+1/3=4/3 of the larger angle.
By proportion,
L+L/3=4L/3=180
L=180*3/4=135 degrees
Smaller angle = L/3=45 degrees
Check: L+L/3=135+45=180 degrees, ok