C1/C2 = 2/3
2pi r1 / 2pi r2 = r1/r2 = 2/3
r1/39 = 2/3
r1 = 39*2/3 = 26
So, your answer is 26cm
The third option, 100*
making it an abtuse triangle
If incorrect, sorry
If you use the distributive property on (x+y)/3, the result should be:
(x/3) + (y/3)
