# Find $x$ in this series of circle!

I truly have no idea what should I do. The only relation I could find is, on circle $$2$$, $$38$$ is equal to $$19\times2$$ (from circle one), and on circle $$3$$, $$72$$ is equal to $$18\times4$$ (from circle one). It was a multiple choice about a question in series of arithmetics, and the choices were $$11, 12, 13, 14,$$ and $$15$$. I just couldn't prove any of the choices.

I didn't know where the source was from, a friend sent it to mine.

• Welcome to puzzling! If you had gotten this puzzle from somewhere else, please state where you've gotten it from! – UnidentifiedX Apr 10 at 2:46
• @Marchotridyo Please accept the answer if it is right. – Aashu Apr 11 at 12:18