## Elementary Technical Mathematics

$11\dfrac{3}{5}$
Note that $18 = 17+1 = 17+\dfrac{5}{5} = 17\dfrac{5}{5}$. Thus, the given expression is equivalent to $=17\dfrac{5}{5} - 6\dfrac{2}{5}$ Subtract the whole number parts and the fraction parts to obtain: $\\(17-6) + (\dfrac{5}{5}-\dfrac{2}{5}) \\=11+\dfrac{3}{5} \\=11\dfrac{3}{5}$