However, I don't see what exactly I should consider given in your picture. Some numbers simply don't work together. (If the large circle has radius 12cm and the small has radius 5cm, I do not think it is possible to have 7 cm where you wrote it between the circles. Also if 3 cm is where you wrote, this would mean 5^2+8^2=12^2. I think I'm getting something wrong - could you clarify the question?)
Hmmm...is smaller circle radius 5, and larger circle radius 12?
If so, then your line = 7 inside circle is impossible.