Calculate moles of B,C and H in 100 grams of compound, ie;
moles B=71.94/10.811
and so on
Then all moles divide by a smallest number of moles, and multiply evrentually by whole nambers, 2 3 to obtain numbers of moles close to whole numbers.
What you did ?
71.94g B * (1mol B / 100g B) = 0.7194mol B
12.07g H * (1mol H / 100g H) = 0.1207mol H
15.99g C * (1mol C / 100g C) = 0.1599mol C
You calculated mass of elements (not moles of elements) in 1 gram of carborane.
The rest of calculations are useless for this problem