Answer
3000 sheets
Work Step by Step
To find the number of sheets you must divide the total height by the thickness of each sheet.
$N=\frac{18\ in}{0.0060\ in/sheet}\longrightarrow$multiply the numerator and denominator by 1000 to make the denominator a whole number
$N=\frac{18\ in}{0.0060\ in/sheet}\times\frac{1000}{10000}$
$N=\frac{18000\ in}{6\ in/sheet}=3000 sheets$
