What's the answer choices? You have to remember that yes, if you were to brute-force the question, it would take you longer than a minute. However, if you were to use all your testtaking skills, you should be able to eliminate answers.
I don't know if they give you a diagram, but if they don't, then the question is even easier because now they're testing you on two things here:
1) What is the relationship between an empirical formula and molecular formula? (empirical formula is the simplified version of the molecular formula, so you know that nicotine's molecula formula must equals some number * C5H7N, so you can already cancel all answers which this doesn't validate)
2) How do you calculate percentage composition of each element. Again here, you don't have to bruteforce the calculation. First think about what you have. You have Carbon, which has an atomic mass of 12. Hydrogen, atomic number of 1, and nitrogen, which is 14. (If you don't know these values are exactly, it's ok, you should still be able to guestimate that carbon has roughly 10 times more than hydrogen, and nitrogen has a little more than carbon.) 12*5 is 60 for carbon, 7 for hydrogen, and 14 for nitrogen. You can round those values to 60, 10, 10, keeping in mind that the hydrogen is overestimated, and nitrogen is underestimated. if you do the fractions after that 60/80 is 3/4 or 75% roughly for carbon, 10/80 = less than 12.5% hydrogen, and 10/80 = more than 12.5% nitrogen. Since you've already likely eliminated 1 or 2 answers from the previous part, you can easily figure out which one of the remaining two has a reasonable answer (for example, if one of your answer puts hydrogen as 47%, you know it's not possible.)
It sounds a bit complicated, but if you adjust your way of thinking and utilize all the skills you have, you can often get away with very little actual calculation. Note how I was less interested in obtaining an exact numerical number as opposed to finding a ballpark figure that allowed me to eliminate answers.
For the record, CaliRX, i did the % composition part of the question in 40 seconds and that's without answers to eliminate.