12.2% of 8600 feet = blank feet
\(\bf {{ a}}\%\ of\ b \implies \cfrac{{{ a}}}{100}\cdot b\implies {{ a}}\div 100\cdot b\\ --------------\\ thus\implies {{ 12.2}}\%\ of\ 8,600 \\\\ \cfrac{{{ 12.2}}}{100}\cdot 8,600\implies {{ 12.2}}\div 100\cdot 8,600\)