Given the incomplete equation representing a reaction:
2c2h14 + o2 --> 12 co2 + 14 h2o
what is the coefficient of o2 when the equation is completely balanced using the smallest whole-number coefficients?
(1) 13(2) 14(3) 19(4) 26

I personally try to balance the equation without looking at the given coefficients in the unbalanced reaction and this is my result:
2 C2H14+11 O2--> 4 CO2+14 H2O
I think none of the given answers are correct, and the answer is obviously 11.
Hope this will help :))

First of all, I'm pretty sure it is impossible to have a compound C2H14, it just won't do according to the rules of organic chemistry. But this is a combustion reaction, and if this is a complete combustion this reaction is not only impossible but illogical as well. Therefore, I encourage that you talk to your teacher about this question :/