Integration - Basic Rules of Definite Integral

Given that \(\displaystyle\displaystyle \displaystyle\int_{-6}^{3} \mathrm{f}(x) \, \mathrm{d}x = 6\), evaluate \(\displaystyle\displaystyle \displaystyle\int_{-6}^{-3} \mathrm{f}(x) - 1 \, \mathrm{d}x + \displaystyle\displaystyle \displaystyle\int_{-3}^{3} \mathrm{f}(x) \, \mathrm{d}x\).