Solve for the missing variable:

ALL FIGURES ARE SIMILAR.
Figure 1: 8m-side 1 and 6m-side 2.
Figure 2: 20m-side 1 and r meters-side 2.
r=?
Solve for r.
Can you help me?
Thank you.

8/20 = 6/r

8 r = 120
r = 120/8 = 15