Okay.. Here is problem 2.
It seems that the questions matches...maybe you saw the wrong answer?
But, to save you some time, let me use my language to reword geno's answer. (none of this is my credit, it is all theirs :D, so you should thank them for creating the answer)
Anyways, since the two circles are externally tangent, that means that line AC is 17 degrees. (add the radii) (you can learn more about tangents here: http://jwilson.coe.uga.edu/EMT668/EMAT6680.2000/Simmons/Assign6/Assign6.html)
Now, since we are looking for BC, we can replace that with a variable, like x.
Using similiar triangles, we see that AX / AC = BY / BC, which means 10 / (17 + x) = 7 / x.
After cross multiplying and simplifying, you will get x = 119/3
(you could view Post 1 for a more in depth solution)